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Jharkhand Board JAC Class 10 Science Important Questions Chapter 8 How do Organisms Reproduce? Important Questions and Answers.

JAC Board Class 10 Science Important Questions Chapter 8 How do Organisms Reproduce?

Additional Questions and Answers

Question 1.
Distinguish between :
(1) Asexual reproduction and Sexual reproduction
OR
What is the basic difference between asexual reproduction and sexual reproduction?
Answer:

Asexual reproduction	Sexual reproduction
1. In asexual reproduction, a single individual is involved, whose certain body part forms the new individual of the same kind.	1. In sexual reproduction, two gametes of opposite sex fuse to form a fertilized egg (zygote) that develops into a new individual.
2. The sex of an organism does not play any role in the reproductive process.	2. The organisms involved are either bisexual or the two individuals are of opposite sex.
3. The new organism has all the characters of the parent organism without any change in the hereditary characters.	3. The new individual follows laws of inheritance and therefore, differs from its parent organisms.
4. Asexual reproduction is of different types such as fission, regeneration, budding, sporulation, fragmentation, etc.	4. No specific types of sexual reproduction.
5. With changing environment asexual reproduction is not sufficient to sustain life.	5. With changing environment, sexual reproduction is essential to sustain life.

(2) Binary fission and Multiple fission
Answer:

Binary fission	Multiple fission
1. Binary fission forms only two offsprings from a single parent.	1. Multiple fission forms many offsprings from a single parent.
2. This method of reproduction occurs in normal condition.	2. This method of reproduction occurs in unfavourable condition.
3. In this method the nucleus divides once.	3. The nucleus divides several times.
4. In this cytoplasm also divides into two parts.	4. In this, small amount of cytoplasm collects around each daughter nuclei after multiple divisions.
5. The parent cell does not get destroyed but it gets divided into two parts.	5. In this with breaking of cyst, the parent cell also break.

(3) Budding and Sporulation
Answer:

Budding	Sporulation
1. In this method of asexual reproduction, a small part of the body of the parent animal grows out as a ‘Bud’.	1. In this method of asexual reproduction, sporangium is produced in the parent plant.
2. The forming bud grows and differentiates in daughter animal.	2. The spore germinates to produce new plant.
3. The forming bud is not a reproductive unit.	3. The spore is the microscopic reproductive unit, which is covered by protective coat.
4. Example: Hydra, Yeast.	4. Example: Mucor, Rhizopus.

(4) Puberty stage in male and Puberty stage in female
Answer:

Puberty stage in male	Puberty stage in female
1. Boys reach puberty at the age of 13 to 14 years.	1. Girls attain puberty at the age of 10 to 12 years.
2. Muscles grow more in boys.	2. Muscles are soft in girls.
3. Voice becomes deep.	3. Voice remains shrilled.
4. Shoulder and chest broadens.	4. The hip region widens.
5. The penis becomes larger and it is capable of becoming erect.	5. Mammary glands, vagina and uterus are developed.

(5) Male reproductive system and Female reproductive system
Answer:

Male reproductive system	Female reproductive system
1. Testes, vas deferens, seminal vesicle, prostate gland and penis are included in it.	1. Ovary, oviduct, uterus and vagina are included in it.
2. Male reproductive system is formed by the organs related to production of sperms and transfer of sperms to the place of fertilisation.	2. Female reproductive system is formed by the organs related to production of ovum, implantation of embryo and child birth.
3. Testes are located in the scrotal sac outside the abdominal cavity.	3. Ovaries are located in the abdominal cavity.
4. The vas deferens, joins with urinary duct coming from urinary bladder to form urethra.	4. The oviducts from two sides open in the muscular uterus.
5. The urethra is common passage for sperms and urine.	5. In female, the urinaiy opening and genital opening are separate.

(6) Contraceptive mechanical method and Contraceptive chemical method
Answer:

Contraceptive mechanical method	Contraceptive chemical method
1. In this method, copper-T, loop, diaphragm worn in vagina and condom are used.	1. In this method, the pills are used which are made up of hormones.
2. This method is useful for both male and female.	2. This method is useful only for females.
3. Sperms are prevented from entering in female genital tract or unable to reach in oviduct due to barrier.	3. Release of ova is inhibited.
4. This method does not affect the production of gametes.	4. This method can disturb the balance of female sex hormones.

Question 2.
Give scientific reasons for the following tatements:
(1) The offsprings formed through asexual : reproduction have same genetic constitution as their parent cell.
Answer:
In asexual reproduction, the union of male and female gametes does not occur.

• Single parent is involved in asexual reproduction. The process of formation of new cell begins s with the creation of DNA copies.
• Two offsprings are formed from the single parent cell which possess equal proportion of DNA.

Hence, the offsprings formed through asexual reproduction have same genetic constitution as their parent cell.

(2) Variation is necessary for the maintenance of existence of any species.
Answer:
Specific species or its population live in the particular environment or habitat which is suitable to them.

• There are changes taking place on earth e.g., fluctuation in temperature, variation in the water level, etc.
• Organisms possesing variations get a chance to urvive in the changing environment.
• Due to variation, organisms can adapt to the environment and hence they can exist through adaptations.
• With the help of variation geographical distribution of organisms increase.

Hence, variation is necessary for the maintenance of existence of any species.

(3) Testes are situated outside the abdominal cavity.
Answer:
Sperms are produced by the testis.

• The temperature of testis remains 2-3°C lower than the body temperature which is optimal for the formation of sperms.
• If testis remain in abdominal cavity, then at the higher temperature, testes are unable to produce sperms.

Hence, testes are situated outside the abdominal cavity.

(4) The number of bryophyllum keep on increasing in garden.
Answer:
In some plants, parts like root, stem and leaves can give rise to buds in dormant state which acts as reproductive unit.

• When suitable moisture and temperature are provided to these dormant structures, they form new plants.
• Buds found on the leaves of bryophyllum induce vegetative propagation.
• In garden, the detatched buds germinate under favourable conditions such as moisture, nutrients, suitable temperature.

Hence, the number of bryophyllum keep on increasing in garden.

(5) The property of vegetative propagation is useful in agricultural purposes.
Answer:
In many plants root, stem and leaves develop into new plants under appropriate condition. Such a mode of reproduction is called vegetative propagation.

Advantages of vegetative propagation are as follow:

• Vegetative propagation is used in layering or grafting methods to grow many plants like sugarcane, roses or grapes for agricultural purposes.
• Plants raised by vegetative propagation can bear flowers and fruits earlier than those produced from seeds.
• The plants that have lost the capacity to produce seeds can also be produced by vegetative propagation, e.g., banana, orange, rose, jasmine
• All plants produced by vegetative propagation are genetically similar to the parent plant.

(6) Extinction of species can be prevented in sexually reproducting organisms.
Answer:
In sexual reproduction, a zygote is formed s by the union of sexual reproductive cells through fertilisation.

• The male reproductive cell is formed in father’s body and female reproductive cell is formed in mother’s body.
• Thus, offspring gets genetic material (DNA) of two different parents. So, there is variation in offspring.
• This variation helps the individual to get adapted to the changing environment. So, organism can live better.
• Through variation and adaptation, species extinction can be prevented and continuity of life is maintained.

So, extinction of species can be prevented in sexually reproducting organisms.

(7) Contraceptive pills are helpful to prevent pregnancy.
Answer:
Pills used for contraception form contraceptive chemical method.

• The female uses oral contraceptive pills.
• The oral pills contain a combination of hormones (progesterone) which stop the release of eggs and fertilisation cannot occur.
• By using, such pills fertilisation can be prevented.

Hence, contraceptive pills are helpful to prevent pregnancy.

(8) The use of ultrasound technique should be banned for the sex determination.
OR
Prenatal sex determination has been prohibited by law.
Answer:
The ultrasound technique should be used for detection of genetic and other structural abnormalities in embryo.

• Some people use the ultrasound technique (sonography) illegally for sex determination of embryo.
• Due to preference to male child the female embryo is aborted.
• The killing of the unborn girl child is known as female foeticide. This sex-selective abortion is unethical and illegal.
• By female foeticide, female sex ratio is reducing at an alarming rate in India.

Hence, the use of ultrasound technique should be banned for the prenatal sex determination.

(9) Each new generation through sexual mode of reproduction will end up in equal number of chromosomes and the DNA content instead of double to its parents.
Answer:
In sexual mode of reproduction, each new generation is the combination of the DNA copies from two parents. Each new generation gets twice the amount of DNA compared to that with the previous generation.

But reduction division i.e., meiosis occurs during gamete formation. As a result germ cells have half the number of chromosomes and half the amount of DNA set as compared to the non- reproductive body cells.

When haploid germ cells from two parents fuse during sexual reproduction, it results in diploid zygote. Chromosomes and the DNA content in new generation is thus reestablished.

Question 3.
Carefully observe the given diagram and answer the questions related with it:

Questions :
(1) Write name of a, b, c, d and e in given diagram.
(2) Where do given events occur?

• Formation of ovum and its release
• Fertilisation
• Implantation of fertilised ovum

(3) The inner wall of uterus….

• Before ovulation and
• What happens if ovum does not get fertilised?

Answer:
(1) a-oviduct, b-ovary, c-uterus, d-cervix, e-vagina

(2)

Event	Organ
(i) Formation of ovum and its release	by ovary
(ii) Fertilisation	in oviduct
(iii) Implantation of fertilised ovum	in uterus

(3) (i) Before ovulation, the inner wall of uterus becomes thick, spongy and with full of blood supply.
(ii) If ovum does not get fertilised, then thick and spongy wall of uterus along with blood and dead ovum comes out of the vagina in the form of bleeding, i.e., Menstruation.

Questions:
(1) Do labelling of a, b, c, d and e in given diagram.

(2) Where do the given events occur?

• Both sperms and urine pass.
• Sperms delivered through in it.
• Add their fluid secretion with sperms.

(3) ‘d’ part passes through which organ?
What changes are noticed in such organ during adolescence?

(4) State the characteristics of cells produced by e in the given diagram.
Answer:
(1) a-seminal vesicle, b-prostate gland, c – vas deferens, d – urethra, e – testis.

(2)

Event	Related organ / part
(i) Both sperms and urine pass	Urethra
(ii) Sperms delivered in it.	Vas deferens
(iii) Add their fluid secretion with sperms	Seminal vesicle, Prostate gland

(3) ‘d’ part is urethra passes through penis. The penis begins to become enlarged and erect. This changes are noticed after puberty.

(4) Sperms are produced by ‘e’ (Testis). The sperms are motile male gametes that consist of mainly genetic material and a long tail.

(1) Identify ‘a’ and state what it carries.
(2) Identify ‘b’ and state the changes in its structure after fertilisation.
(3) Identify ‘c’ and mention from where is it released and by which process does it reach here.
(4) Identify ‘d’ and state how seeds are formed?
Answer:
(1) a – Pollen tube, it carries male germ cell.
(2) b – Ovary, it grows rapidly and ripens to form a fruit after fertilisation.
(3) c – Pollen grain, it is released from anther of stamen and by the process of pollination it reaches on the stigma.
(4) d – Female germ cell, male germ cell fuses with it to form zygote. Zygote divides several times to form an embryo within the ovule. The ovule develops a tough coat and it is gradually converted into seed.

Objective Questions and Answers

Question 1.
Answer the following questions in short:
(1) Write down the name of different methods of asexual reproduction.
Answer:
The various methods of asexual reproduction are:

• Fission (Binary fission and multiple fission)
• Fragmentation
• Regeneration
• Spore formation and
• Vegetative propagation.

(2) Name two animals which reproduce asexually through fission.
Answer:
Animals that reproduce asexually through fission : Amoeba. Plasmodium.

(3) Name the asexual method of reproduction in (a) Hydra and (b) Plasmodium.
Answer:

• In hydra methods of asexual reproduction are regeneration and budding.
• In plasmodium method of asexual reproduction is multiple fission.

(4) What is the meaning of regeneration? Name two animals which can regenerate from their body parts.
Answer:
Meaning of regeneration : A small cut part of the body can regenerate to form a complete new organism.
Example: Hydra and Planaria.

(5) What is the meaning of vegetative propagation?
Answer:
Vegetative propagation means production of new plants from the roots, stem or leaves of parental plant without taking help of any reproductive orgAnswer:

(6) How do we know that two different individual organisms belong to the same species?
Answer:
Due to similarities among organisms it is clear that they belong to the same species.

(7) What will lead to change in body designs?
Answer:
The DNA in the cell nucleus is the information source for making proteins. If the information is changed, different proteins are formed leading changes in body designs.

(8) What does most basic level in reproduction involve?
Answer:
The most basic level in reproduction involves making of DNA copies for the blueprints of body design.

(9) When does the newly formed DNA copies separate?
Answer:
Newly formed DNA copies separate when additional cellular apparatus is formed at the time of cell division.

(10) Are the two cells formed by a cell division absolutely identical?
Answer:
No, the process of copying the DNA will have some variations each time. As a result, the DNA copies generated may not be identical to \ the original. So, the two cells are not absolutely identical.

(11) How is reproduction to be achieved from a single type, if the organism itself consists of many cell types?
Answer:
Organism may contain many cells but only specialized cells are able to perform reproduction.

(12) Why regeneration is not the same as reproduction?
Answer:
Reproduction is a complex process using specialised cells or organs but regeneration is basically a repair process in which torn out part can heal.

(13) Which parts of flowers fall off after fertilisation?
Answer:
The petals, sepals, stamens, style and stigma may shrivel and fall off after fertilisation.

(14) What are the functions of petals and sepals?
Answer:

• Function of petals : To attract insects for pollination.
• Function of sepals : To protect petals, stamens and pistils.

(15) Which part of flower persists in the fruit of which plant?
Answer:
Dry sepals persist in some fruits such as brinjals, apple, guava. Some of sepals persist in strawberry.

(16) State any two changes that can be included under the general process of growth in human beings.
Answer:
Increase in height and weight, replacement of milk teeth by permanent teeth, etc.

(17) How are new combinations of variants produced generation after generation?
Answer:
Each new variation is made in a DNA copy that already has variation accumulated from previous generations. During sexual reproduction, variations from two individuals are recombined.

(18) Name the methods in which property of vegetative propagation is used? Give the examples for the same.
Answer:
The property of vegetative propagation is used in layering and grafting methods. Sugarcane, roses, grapes are grown for agricultural purposes by this methods.

(19) By which agents is cross-pollination achieved?
Answer:
Cross-pollination is achieved by agents like wind, water or animals.

(20) State any two common changes that appear in both sexes during the period of adolescence?
Answer:
Thick hair growing in armpits and the genital area, the skin frequently becomes oily and pimples begin to develop.

(21) Secretion of which glands makes transport and nutrition of sperms easier?
Answer:
The fluid secretion of prostate gland and seminal vesicles makes transport and nutrition of sperms easier.

(22) State the difference in meaning between zygote, embryo and foetus.
Answer:

Zygote	Embryo	Fbetus
1. The ferti-lised egg is called zygote. 2. It is formed by fusion of sperm and egg cell.	The zygote starts dividing and form a ball of cells called embryo.	The em-bryo is implanted in the lining of the uterus where it continues to grow organs then it is called foetus.

(23) What is called placenta?
Answer:
A disc-like special tissue embedded in uterine wall through which the embryo gets nutrition from mother’s blood is called placenta.

(24) How is body of mother designed to undertake the development of the child?
Answer:
The uterus in mother prepares itself every month to receive and nurture the growing embryo.

(25) How the transmission of sexually transmitted diseases can be prevented during the sexual act?
Answer:
Using a condom diming sexual act can help to prevent transmission of sexually transmitted diseases.

(26) State the names of STDs caused by bacteria and virus.
Answer:
Bacterial STDs : Gonorrhoea, Syphilis.
Viral STDs: Warts, HIV-AIDS

(27) What is the misuse of prenatal sex determination?
Answer:
Parents terminate the pregnancy after knowing the sex of their unborn child; usually a daughter. This is illegal and unethical to carry out prenatal sex determination for aborting female foetus.

Question 2.
Define : OR Explain the terms :
(1) Reproduction
Answer:
The process producing new organism of its own kind during their maturity stage is known as reproduction.

(2) Variation
Answer:
The difference in the characters of individuals of a same species or its population is known as variation.

(3) Asexual reproduction
Answer:
The mode of reproduction allows new generation to be created from a single individual without the formation and fusion of gametes is known as asexual reproduction.

(4) Sexual reproduction
Answer:
A mode of reproduction that depend on the involvement of two individuals (male and female) to create new generation is known as sexual reproduction.

(5) Multiple fission
Answer:
A mode of asexual reproduction in which the division of parent cell forms small, nearly equal sized daughter offsprings is known as multiple fission.

(6) Fragmentation
Answer:
The breaking up of the body of a multi-cellular organism into two or many pieces and on maturing, each piece grows to form a complete new organism is known as fragmentation.

(7) Bud
Answer:
A bulging structure that develops as an outgrowth due to repeated cell division at one specific site, which develops into tiny individual is called a bud.

(8) Vegetative propagation
Answer:
In certain plants, root, stem and leaves develop into new plants under favourable conditions. This property is called as vegetative c propagation.

(9) Sporangia
Answer:
In fungus e.g., Rhizopus, tiny blob-like structure producing spores for reproduction is called sporangia.

(10) Spore
Answer:
A microscopic reproductive unit produced in sporangia and covered by thick protective wall is called spore.

(11) Meiosis
Answer:
A type of cell division in germ cells in which chromosome number is reduced to half is called meiosis.

(12) Flower
Answer:
A sexual reproductive structure produced in flowering plants, especially in angiosperms is called flower.

(13) Seed germination
Answer:
The development of new plant from the seed upon getting favourable conditions, is known as seed germination.

(14) Pollination
Answer:
A process of transfer of pollen from anther of a stamen to the stigma of a pistil in the same or in different flower is called pollination.

(15) Puberty
Answer:
The age at which reproductive organs become functional and attaining the sexual maturity is known as ‘puberty’.

(16) Female foeticide
Answer:
Illegal sex-selective abortion of female foetuses or killing the female foetus is called female foeticide.

(17) Fertilisation
Answer:
A process of a fusion of male gamete and female gamete to form a zygote is called fertilisation.

(18) Menstruation
Answer:
Menstruation is the periodic event taking place after every 28 days in mature woman. This is a cyclic process, interrupted only by pregnancy. During menstruation there is bleeding through vaginal opening. The cell debris and unfertilised ovum is given out of the body during menstruation.

If the egg is not fertilised, it lives for about one day. Since the ovary releases one egg every month, the uterus also prepares itself every month to receive a fertilised egg. Uterine lining becomes thick, spongy and richly supplied with blood. But if fertilisation does not occur then this lining is not needed any longer. So, the lining slowly breaks and comes out through the vaginal opening as blood and mucous.

This cycle takes place roughly every month and is called menstruation. It usually lasts for about two to eight days.

some degree of sexual maturation does not necessarily mean that the body or the mind is ready for sexual acts or for having and bringing up children.

Question 3.
Fill in the blanks :

1. ……………….. undergoes continuous cell division to produce multicellular embryo.
2. ……………….. is the causative agent responsible for sexual diseases like gonorrhea and syphilis.
3. ……………….. type of cell division reduces chromosome number to half in germ cells.
4. In plasmodium, asexual reproduction occurs through ………………..
5. On the surface of potato tuber, there are many ……………….. present for the asexual reproduction.
6. A small cut part of organism’s body can form complete new organism. This process is known as ………………..
7. In flowering plant, fertilisation of egg cell occur in ………………..
8. In sexual reproduction, creation of diversity in characters are fulfilled by ………………..
9. In female, every ……………….. days ovum is released from the ovary.
10. To prevent pregnancy, copper-T is placed in ………………..
11. The temperature of scrotum remains ……………….. below the body temperature.
12. The genetic variation created during reproduction is the basis for ………………..
13. In flowering plant, ……………….. is most important part for continuity of life.
14. The cells involved in sexual reproduction are known as ………………..
15. When sperms reach in urethra from testes, secretions from ……………….. and ……………….. are added with them.
16. If fertilisation of ovum does not occur in female, then ……………….. happens.
17. The size of ……………….. is determined by the rates of birth and death.
18. The uterus opens into the vagina through the ………………..
19. A ……………….. is a future shoot and a ……………….. is a future root in the structure of seed.
20. The DNA in the cell nucleus is the information source for making ………………..

Answer:

1. Zygote
2. Bacteria
3. Meiosis
4. multiple fission
5. buds
6. regeneration
7. ovule
8. Genetic variation
9. 28
10. uterus
11. 2-3°C
12. evolution
13. ovule
14. gametes/germ cells
15. seminal vesicles, prostate gland
16. menstruation
17. population
18. cervix
19. plumule, radicle
20. proteins

Question 4.
State whether the following statements are true or false:

1. Number of organisms increase rapidly through asexual reproduction under unfavourable condition.
2. Fragmentation is the simplest method of reproduction in unicellular animals like amoeba and leishmania.
3. The information of protein synthesis is stored in DNA of a cell nucleus.
4. Variation is useful for the survival of species.
5. Budding is an asexual reproduction method observed only in animals.
6. Condom is a mechanical barrier.
7. In sexual reproduction, DNA content is doubled in zygote than the DNA content of parents.
8. The pollen grains produced in stamen are male reproductive cells.
9. Secretion of the sex hormones starts at the puberty stage.
10. Fallopian tubes come out from the vas deferens.
11. In human, fertilisation occurs in vagina of female and embryo development occurs in uterus.
12. The ovaries contain thousands of immature eggs in newborn girl.
13. Menstruation usually lasts for about two to eight days.
14. Prenatal sex determination is legal in our country.
15. The size of population is determined through birthrate and deathrate of organisms.
16. Syphilis is a STD.
17. Copying of DNA is a part of cellular reproduction.
18. Plants such as banana, orange, rose and jasmine that have lost the capacity to produce s seeds can reproduce by vegetative propagation.
19. Self-pollination is considered better than cross-pollination as far as variation is concerned.
20. Reproduction by production of bud is a common in yeast, hydra and bryophyllum.

Answer:

1. False
2. False
3. True
4. True
5. False
6. True
7. False
8. False
9. True
10. False
11. False
12. True
13. True
14. False
15. True
16. True
17. True
18. True
19. False
20. True

Question 5.
Match the following :
(1)

Column I	Column II
1. Fragmentation	p. Planar ia
2. Budding	q. Potato
3. Vegetative propagation	r. Spirogyra
4. Regeneration	s. Yeast

Answer:
(1 – r), (2 – s), (3 – q), (4 – p).

(2)

Column I	Column II
1. Testis	p. Mouth of uterus
2. Ovary	q. Testosterone
3. Prostate gland	r. Fertilisation
4. Cervix	s. Disc-like special tissue develops between embryo and the uterus wall.
5. Oviduct	t. Progesterone
6. Placenta	u. Secretory gland in the passage of sperms

Answer:
(1 – q), (2 – t), (3 – u), (4 – p), (5 – r), (6 – s).

(3)

Column I	Column II
1. Binary fission	p. Hydra
2. Multiple fission	q. Amoeba
3. Budding	r. Rhizopus
4. Spore formation	s. Plasmodium

Answer:
(1 – q), (2 – s), (3 – p), (4 – r).

(4)

Column I	Column II
1. Ovary	p. Fertilisation of ovum by a sperm
2. Oviduct	q. Passage of sperms
3. Uterus	r. Secretion of sex hormones
4. Vagina	s. Growth of fertilised ovum and development of embryo

Answer:
(1 – r), (2 – p), (3 – s), (4 – q).

(5)

Column I	Column II
1. Life of unfertilised egg	p. 2 to 8 days
2. Puberty in girls	q. About 1 day
3. Menstruation in female	r. At least 9 months
4. Development of embryo in uterus of female	s. 10 to 12 years

Answer:
(1 – q), (2 – s), (3 – p), (4 – r).

(6)

Column I (Contraceptive methods)	Column II (Uses)
1. Barrier method in male	p. Oral pills
2. Chemical method	q. Condom
3. Surgical method	r. Copper-T
4. Barrier method in female	s. Fallopian tubes blocked

Answer:
(1 – q), (2 – p), (3 – s), (4 – r).

Question 6.
Diagram based questions:
1. Identify organisms in the diagram. Which asexual reproduction method is seen? Write it.

Answer:

• Leishmania – Binary fission
• Plasmodium – Multiple fission
• Spirogyra – Fragmentation
• Planaria – Regeneration

2. Draw labelled diagram of (b) and (c) steps of budding in hydra.

Answer:

3. In amoeba, binary fission’s some diagrams are given. Give its proper sequence.

Answer:
(3) → (2) → (1) → (4)

4. Carefully observe the given diagrams and give answer of following questions:

(1) Identify organisms (a), (b), (c), (d) and write their names.
(2) Give names of biological processes seen in all the four diagrams.
(3) How is this biological process useful for organisms?
Answer:
(1)

• Hydra
• Rhizopus
• Bryophyllum
• Planaria

(2) Asexual reproduction

• Budding
• Spore formation
• Vegetative propagation
• Regeneration

(3 ) To maintain continuity of life and to increase their number

5. Identify the given diagram and label the parts a, b and c.

Answer:
Spore formation in Rhizopus
a-Sporangium, b-Spore and c-Hyphae

6. Observe the diagram and answer the questions :

Which part give rise to shoot when seed germinates?
(1) Is the seed dicot or monocot?
(2) Which part give rise to shoot when seed germinates?
(3) Identify ‘a’ in the diagram.
Answer:
(1) Dicot
(2) Plumule
(3) a – Radicle

Question 7.
Select the correct option from those given below each question:
1. A simple multicellular animal having tentacles and lives in fresh water reproduces by the asexual method of ………………………
A. binary fission
B. spore formation
C. budding
D. fragmentation
Answer:
C. budding

2. In which of the following living organism spore formation takes place?
A. Rhizopus
B. Planaria
C. Spirogyra
D. Potato
Answer:
A. Rhizopus

3. Method of asexual reproduction in spirogyra….
A. division of a cell into two cells
B. breaking up of filaments into smaller bits
C. division of a cell into many cells
D. formation of a large number of buds
Answer:
B. breaking up of filaments into smaller bits

4. The filaments of certain algae breaks again and again and each part develops as individual algae. Which type of process is this?
A. Budding
B. Fragmentation
C. Binary fission
D. Multiple fission
Answer:
B. Fragmentation

5. Which kind of reproduction methods are fission, budding, spore formation, etc.?
A. Vegetative propagation
B. Asexual reproduction
C. Sexual reproduction
D. None of these
Answer:
B. Asexual reproduction

6. Which parts of plant produce new plant through vegetative propagation?
A. Root, stem and flower
B. Stem, flower and fruit
C. Stem, leaf and flower
D. Root, stem and leaf
Answer:
D. Root, stem and leaf

7. For how many days does the menstruation period last in woman?
A. 2 to 8
B. 10 to 12
C. 13 to 18
D. 28 to 32
Answer:
A. 2 to 8

8. Which unicellular fungus shows budding?
A. Mucor
B. Yeast
C. Amoeba
D. None of these
Answer:
B. Yeast

9. Which of the following organism shows regeneration?
A. Amoeba
B. Paramoecium
C. Hydra (or Planaria)
D. Rhizopus
Answer:
C. Hydra (or Planaria)

10. Where are testes located in male?
A. In abdominal cavity
B. In vas deferens
C. In scrotum
D. In penis
Answer:
C. In scrotum

11. If the normal temperature of the body is 37 °C, then the ideal temperature of the scrotum is ………………
A. 37 °C
B. 36 °C
C. 39 °C
D. 34 °C
Answer:
D. 34 °C

12. Where does the fertilisation of sperm and ovum occur in human?
A. In uterus
B. In cervix
C. In vagina
D. In oviduct
Answer:
D. In oviduct

13. Where does the implantation and development of the embryo take place?
A. In uterus
B. In vagina
C. In ovary
D. In oviduct
Answer:
A. In uterus

14. Duration from time of fertilisation in human female to the birth of a child :
A. 100 days
B. 180 days
C. 210 days
D. 280 days
Answer:
D. 280 days

15. Which structure develops between uterine wall and foetus to fulfill the need of nutrition?
A. Placenta
B. Umbilical cord
C. Amnion
D. Amniotic fluid
Answer:
A. Placenta

16. In asexual reproduction, offsprings are similar, because…
A. only one parent is involved in reproduction.
B. two parents are involved in reproduction.
C. reproductive cells are involved.
D. reproductive cells are not involved.
Answer:
A. only one parent is involved in reproduction.

17. From the following, which fungus does not undergo asexual reproduction through spore formation?
A. Rhizopus
B. Penicillium
C. Yeast
D. Mucor
Answer:
C. Yeast

18. What is the similarity in reproduction between amoeba and bacteria?
(1) They are multicellular.
(2) They are unicellular.
(3) They only undergo sexual reproduction.
(4) They only undergo asexual reproduction.
(5) They mainly undergo binary fission.
A. (1), (3) and (4)
B. (2) and (3)
C. (2) and (4)
D. (2), (4) and (5)
Answer:
D. (2), (4) and (5)

19. Which is a necessity of cellular reproduction?
A. Changes in niche
B. Continuity of life
C. Copying of DNA
D. Transportation of hereditary characters
Answer:
C. Copying of DNA

20. Which of the following is true for the flower?
(1) Flowers are always bisexual.
(2) They possess sexual reproductive part.
(3) They are produced in all plant groups.
(4) Its ovule after fertilisation is converted into seed.
A. (1) and (3)
B. (2) and (3)
C. (1) and (4)
D. (2) and (4)
Answer:
D. (2) and (4)

21. Variation is observed more in the offsprings produced through sexual reproduction, because…
A. sexual reproduction is a long and complicated process.
B. genetic material of two parents of different species is inherited in offspring.
C. genetic material of two parents of same species is inherited in offspring.
D. genetic material in the offspring is double than that in the parent.
Answer:
C. genetic material of two parents of same species is inherited in offspring.

22. In which part of the flower male reproductive cells and female reproductive cells are produced I respectively?
A. Pollen grain, ovule
B. Anther, Stigma
C. Stigma, style
D. Ovary, ovule
Answer:
A. Pollen grain, ovule

23. What will be produced from the fertilised egg cell In a flower?
A. Embryo
B. Spore
C. Fruit
D. All of given
Answer:
A. Embryo

24. In which type of reproduction there is seed formation?
A. Vegetative propagation
B. Asexual reproduction
C. Sexual reproduction
D. Budding
Answer:
C. Sexual reproduction

25. At the stage of puberty in boy there are secondary sexual changes. Which of the following is these?
A. Increase in height and weight
B. Hair growth in armpits
C. Hair growth in genital area
D. Larger and erect penis
Answer:
D. Larger and erect penis

26. For the formation of sperms in testes, the temperature…
A. must be lower than the body temperature.
B. must be higher than the body temperature.
C. must be same as the body temperature.
D. temperature is not an affecting factor.
Answer:
A. must be lower than the body temperature.

27. Which of the following are not the functions of testes, at puberty?
(1) Formation of reproductive cells
(2) Development of placenta
(3) Secretion of testosterone
(4) Secretion of progesterone
A. (1) and (4)
B. (2) and (4)
C. (3) and (4)
D. (2) and (3)
Answer:
B. (2) and (4)

28. Which of the following group of sexual diseases occur through the bacteria?
A. AIDS-Herpes of reproductive organs
B. Syphilis-Gonorrhea
C. Syphilis-AIDS
D. Gonorrhea-AIDS
Answer:
B. Syphilis-Gonorrhea

29. Offsprings formed by organisms showing asexual reproduction have greater range of similarity because …
(1) only one parent is involved in asexual reproduction.
(2) reproductive cells does not involve in asexual reproduction.
(3) asexual reproduction is faster than sexual reproduction.
(4) more offsprings are produced in asexual reproduction.
A. (1) and (2)
B. (1) and (3)
C. (2) and (4)
D. (3) and (4)
Answer:
B. (1) and (3)

30. Stamen in flower:
A. They produce new seeds.
B. They produce new fruit.
C. They produce pollen grains.
D. They develops fertilised ovum.
Answer:
C. They produce pollen grains.

31. The responsible factors for rapid spread of rhizopus on piece of bread are….
(1) more amount of spores.
(2) getting moist and mineral nutrients from the bread.
(3) presence of branched tubular hyphae.
(4) round spores having sporangium.
A. (1) and (3)
B. (2) and (4)
C. (1) and (2)
D. (3) and (4)
Answer:
C. (1) and (2)

32. What is indicated by the given figure?

A. Budding in yeast
B. Formation of pseudopodia in amoeba
C. Binary fission in amoeba
D. Cyst-formation in amoeba
Answer:
C. Binary fission in amoeba

33. Which is the sign of initiation of reproductive maturity in girl?
A. When menstruation occurs
B. When embryo is carried
C. When she arrives at menopause stage
D. Before ovulation
Answer:
A. When menstruation occurs

34. Which part of flower becomes mature and modified into fruit?
A. Ovule
B. Carpel
C. Ovary
D. Female gamete
Answer:
C. Ovary

35. When plants lose the capacity of seed formation then how does reproduction occur in them?
A. By spore formation
B. By vegetative propagation
C. By fission
D. By regeneration
Answer:
B. By vegetative propagation

36. In which contraceptive method, condom is used?
A. Surgical method
B. Hormonal method
C. Chemical method
D. Mechanical method
Answer:
D. Mechanical method

37. Statement A: Prenatal sex determination has been prohibited by law.
Reason R : Illegal sex-selective abortion of female foetuses increased.
Which is the correct option for A and R?
A. Both A and R correct, R is correct explanation of A.?
B. Both A and R correct, but R is not explanation of A.?
C. A is correct, R is incorrect.
D. A is incorrect, R is correct.
Answer:
A. Both A and R correct, R is correct explanation of A.

Question 7.
Answer as directed : (Miscellaneous)
(1) Give full form : HIV – AIDS
Answer:
HIV : Human Immunodeficiency Virus
AIDS: Acquired Immuno Deficiency Syndrome

(2) Following events in flowering plants given below:
(a) Pollen tube develops in style
(b) Plumule develops as shoot system
(c) Ovule modified in seed
(d) Anther releases pollen and stigma receives it.
Arrange them in correct sequence.
Answer:
(d) → (a) → (c) → (b)

(3) Identify me : I am a type of cell division, significant during sexual reproduction and helping to maintain constant chromosome number generation after generation in particular species.
Answer:
Meiosis

(4) Stamen : Pollen grains : : Testes : ………………
Answer:
Sperms

(5) Find mismatched pair :
A. Hydra → Budding, Regeneration
B. Binary fission → Amoeba, Leishmania
C. Pistil → Anther, Filament
D. Sperms → Genetic material, Long tail
Answer:
C. Pistil → Anther, Filament

(6) Identify me : I am a disc like specialised tissue developed after implantation of embryo in a uterine wall.
Answer:
Placenta

(7) Arrange following events in correct sequence:
(a) Menstruation lasts for two to eight days.
(b) Ovary releases one egg every month.
(c) Uterus lining becomes thick and spongy.
(d) Egg is not fertilised.
Answer:
(b) → (c) → (d) → (a)

(8) Differentiate the word pair : Uterus and urethra
Answer:
Uterus is an elastic bag like structure in female reproductive system where embryo is implanted and nourished.
Urethra is a common passage for passing sperms and urine in males.

(9) Plasmodium : malaria : ………………….. : :
Leishmania : ………………….. : Binary fission
Answer:
Multiple fission, Kala-azar

(10) Arrange following events in correct sequence :
(a) Division of zygote to form embryo.
(b) Rhythmic contractions of muscles in the uterus.
(c) The lining of uterus thicken and richly supplied with blood.
(d) Embryo develops organs to become foetus.
(e) Embryo gets nutrition with the help of placenta.
Answer:
(c) → (a) → (e) → (d) → (b)

(11) Find mismatched pair :
(I) Viral infection Warts
(II) Bacterial infection – Syphilis
(III) Fungal infection – Kala-azar
(IV) Protozoan infection – Malaria
Answer:
(III) Fungal infection Kala-azar

(12) Identify me : I am an external organ of male reproductive system essential for sexual intercourse, but due to covering on me, unwanted pregnancy and transmission of many infection can be prevented.
Answer:
Penis

Value Based Questions With Answers

Question 1.
In higher level multicellular animals, the capacity of regeneration is seen or not? Justify your answer with an example of human body. Is it a type of reproduction?
Answer:
Yes, in human being hair and nails grow after cutting. At a site of injury, new cells are formed and healing of cut body part takes place. But this is not a type of reproduction.

Question 2.
A woman has undergone surgical contraceptive method. Will she show the menstruation or not? Justify your answer.
Answer:
Yes, she will show menstruation till 45 – 48 years. Because oviducts are surgically s blocked whereas menstruation flow takes place mainly due to breakage of lining of uterine wall. This is under the influence of ovarian hormones.

Question 3.
A man has undergone surgical contraceptive method. Will he be able to participate in sexual act? On which structure/part, surgical process s is done? Will he now be safe against sexually transmitted diseases?
Answer:
Yes, man will be able to participate in sexual act even after he has undergone surgical contraceptive method.
Vas deferens is surgically blocked.
He will not be safe against sexually transmitted diseases unless he uses condom.

Question 4.
Why in sexual reproduction variation is observed even though the DNA and chromosomes do not get doubled?
Answer:
Variation is observed in offsprings produced through sexual reproduction because off-springs receive DNA and chromosomes from two different parents.
New variation is made in DNA copying in parental generation and during gamete formation, meiosis is also responsible for new combinations.

Question 5.
Vegetative propagation is seen in which plants? Flowering or non-flowering plant?
Artificial vegetative propagation is practised in which plants? Seed bearing or seedless plants?
Answer:
Vegetative propagation is seen mainly in flowering plants. But non-flowering plants such as moss, fern also show vegetative propagation.

Artificial vegetative propagation is practised in seed bearing plants such as rose, sugarcane, grapes, jasmine, orange, etc.

Practical Skill Based Questions With Answers

Question 1.
Collect different flowers such as Maize, Sunflower, Papaya, Hibiscus, Datura, Rose, Crinum, etc. Which of them are bisexual? Draw diagram of any one bisexual flower and state function of each parts.
Answer:
Bisexual flowers: Hibiscus, Sunflower, Datura, Rose, Crinum.

Question 2.
You are given following seeds :
Maize, Bean, Wheat, Green gram (Mung), Rice, Groundnut.
Classify them into monocot and dicot seeds. Select any one dicot seed and dip in water for about 4 to 5 hours. Press it and observe the part of embryo.
Questions:
(1) Are the basic structural parts of an embryo equal in all dicot seeds?
(2) What is the function of cotyledons?
(3) Is there any change in size of cotyledon as seed germination progresses?
Answer:
Monocot seeds : Maize, Wheat, Rice
Dicot seeds : Bean, Green gram (Mung). Groundnut

(1) Yes
(2) Cotyledons of dicot seeds are food storing. It provies nutrients to germinating seeds.
(3 ) The size of cotyledons is reduced as the seed germination progresses. The food stored in cotyledons is used for

Question 3.

Identify diagram (a), (b), (c) and (d) and give its name.
Out of these, which one is effective for preventing unwanted pregnancy as well as for protection against sexually transmitted diseases ?
Answer:
(a) Condom
(b) Copper-T
(c) Surgical contraceptive for male (vasectomy)
(d) Surgical contraceptive for female (tubectomy).
Only condom is effective for preventing unwanted pregnancy as well as for protection against sexually transmission of diseases.

Memory Map

Students must go through these JAC Class 10 Science Notes Chapter 6 Life Processes to get a clear insight into all the important concepts.

JAC Board Class 10 Science Notes Chapter 6 Life Processes

→ Indication of life : Showing movements is an indication of life. Movements can be visible or invisible. They can be related to growth or not concerned with growth.

• Viruses are said to be connecting link between living and non-living.

→ Life processes: The main processes, that are carried out by all the living organisms in order to sustain their existence as living beings, are called life processes.

• Common life processes: The common life processes occurring in all the living organisms are nutrition, respiration, excretion or removal of metabolic wastes, growth, transportation, movement, control and coordination, reproduction, etc.

→ Nutrition: A process to transfer a source of energy from outside the body of the organism to the inside is called nutrition.

→ Modes of nutrition: There are mainly two modes of nutrition:
(i) Autotrophic nutrition : The organisms, that possess chlorophyll utilize solar energy, water and carbon dioxide and synthesize their own food as glucose -a simple form of carbohydrate. This process is called photosynthesis.

• The photosynthetic organisms show autotrophic nutrition. Green plants and certain photosynthetic bacteria are autotrophic organisms.
• Equation of photosynthesis:
  
• The carbohydrates, i.e., glucose which are not used immediately are stored in . form of starch, in case of plants.

(ii) Heterotrophic nutrition : Organisms which consume complex food material prepared by other organisms are called heterotrophic organisms. They lack chlorophyll and thus cannot synthesise their own food. All animals, fungi, cuscuta, etc. are heterotrophic organisms.

→ Digestion : Process of converting complex food components into simple and soluble form with the help of enzymes is called digestion. The resulting nutrients can be easily absorbed after digestion.

• Digestion is essential for nutrition especially. for animals.
• In single celled animals example : (Amoeba, Paramoecium), intracellular digestion takes place and in human beings digestion is extracellular in alimentary canal.
• Human alimentary canal: It extends from mouth to anus consisting of buccal cavity, oesophagus, stomach, small intestine, large intestine. There are associated glands with alimentary canal which help in digestion.
• Salivary glands, liver and pancreas are accessory glands.
• In human beings five different digestive juices, i.e., saliva, gastric juice, bile juice, pancreatic juice and intestinal juice play significant role in the process of digestion.
• Small intestine is the longest part of the alimentary canal of a human. However the length of the small intestine depends on the food consumed by the animal. Example: Herbivores have a longer small intestine, carnivores have a shorter small intestine.
• Villi: The inner lining of the small intestine has numerous finger like projections called villi which increase the surface area for absorption of simple nutrients formed by digestion.

→ Respiration : A process of breakdown of simple carbohydrates such as glucose to liberate energy is called respiration. As this process occurs inside the living cells, it is also known as cellular respiration. The energy released during respiration is stored in ATP.

• ATP is the energy currency for most of cellular processes.

→ Types of respiration: (1) Aerobic respiration: Respiration in presence of oxygen. (2) Anaerobic respiration : Respiration in absence of oxygen.
The release of energy in the aerobic respiration is greater than in the anaerobic respiration.

• Aerobic organisms need sufficient O₂ and they expell CO₂ during the process.
• Plants exchange gases through stomata. Stomata are tiny pores present on the lower surface of the leaves.
• Breathing is an important process in animals for aerobic respiration. The rate of breathing in aquatic animals is much faster than that seen in terrestrial animals.

→ Human respiratory system : This system consists nostrils, pharynx, larynx, trachea bronchi and bronchioles and lungs. Each bronchiole ends in alveolus. In lungs, large number of balloon-like structure alveoli are present. The alveoli provide a surface for gaseous exchange. In human beings a respiratory pigment haemoglobin present in red blood corpuscles take up oxygen from the air in the lungs and carry it to tissues.

→ Blood : Blood is a fluid connective tissue that carries out transportation of many substances in human beings. Blood consists of plasma which is fluid in which blood corpuscles i.e., red blood corpuscles, white blood corpuscles and platlets are suspended. Red blood corpuscles carry oxygen. Platelets plug blood leakage by helping to clot the blood at the point of injury.

• Human heart is conical, muscular organ which is four chambered, consisting of two atria (auricles) and two ventricles. There is oxygenated blood in left chambers of the heart whereas there is deoxygenated blood in right chambers.
• Fishes have only two chambered heart. Amphibians and most of the reptiles have three chambered hearts.
• Blood vessels : The blood vessels are arteries, veins and blood capillaries. In the arteries, the blood flows from the heart towards different organs and in the veins, blood flows from different organs towards the heart.

→ Lymph: It is another type of fluid involved in transportation similar to the blood plasma but it is colourless and contains less protein.

→ Transportation in plants:

• In higher plants, the transportation of water and mineral elements takes place through xylem and that of synthesized organic substances takes place through phloem.
• Conducting components of xylem: Tracheids and tracheae (vessels).
• Conducting components of phloem: Sieve tubes and companion cells.
• In xylem the conduction of materials starts from the root in upward direction, while in phloem the conduction of materials occurs in both the directions viz. downward from above and upward from roots.
• In higher plants, the water in the tracheids and tracheae is pulled upwards due to the suction force created as a result of transpiration.
• The effect of root pressure in transport of water is more important at night.
• Transpiration : The loss of water in form of water vapour from the aerial parts of the plant is called transpiration.
• Translocation of organic food : The transport of soluble products of Photosynthesis through the phloem tissue is called translocation. In this process ATP is used.

→ Excretion : The biological process of removal of harmful nitrogenous metabolic wastes from body is called excretion. Many unicellular organisms remove nitrogenous wastes by simple diffusion from the body surface.

→ Human excretory system : It consists of a pair of kidneys, a pair of ureters, urinary bladder and a urethra.
Each kidney has large number of the basic filtration units called nephrons.

→ Excretion in plants: Plants use completely different strategies for excretion than those of animals.
Waste material may be stored in the cell- vacuoles or as gum and resin, removed in the falling leaves, or excreted into the surrounding soil.

Jharkhand Board JAC Class 10 Maths Solutions Chapter 14 सांख्यिकी Ex 14.2 Textbook Exercise Questions and Answers.

JAC Board Class 10 Maths Solutions Chapter 14 सांख्यिकी Exercise 14.2

प्रश्न 1.
निम्नलिखित सारणी किसी अस्पताल में एक विशेष वर्ष में भर्ती हुए रोगियों की आयु को दर्शाती है :

उपर्युक्त आँकड़ों से बहुलक और माध्य ज्ञात कीजिए। दोनों केन्द्रीय प्रवृत्ति की मापों की तुलना कीजिए और उनकी व्याख्या कीजिए।
हल :
बहुलक के लिए :
यहाँ अधिकतम बारम्बारता 23 है। इसका संगत वर्ग अन्तराल 35-45 है।
∴ बहुलक वर्ग 35-45 होगा
∴ l = 35, f₁ = 23, f₀ = 21, f₂ = 14 और h = 10

अतः बहुलक = 36.8 वर्ष

माध्य के लिए-

माना कल्पित माध्य (A) = 40 है।

अतः आँकड़ों का बहुलक = 36.8 वर्ष तथा माध्य = 35.375 वर्ष
अस्पताल में भर्ती अधिकतम् रोगी 36.8 वर्ष आयु (लगभग) के हैं। जबकि औसतन अस्पताल में भर्ती किए गए रोगियों की आयु 35.57 वर्ष है।

प्रश्न 2.
निम्नलिखित आँकड़े, 225 बिजली उपकरणों के प्रेक्षित जीवन काल (घण्टों में) की सूचना देते हैं:

उपकरणों का बहुलक जीवन काल ज्ञात कीजिए।
हल :
यहाँ अधिकतम बारम्बारता 61 है। इसका संगत वर्ग अन्तराल 60-80 हैं:
∴ बहुलक वर्ग = 60-80
l = 60, f₁ = 61, f₀ = 52, f₂ = 38 और h = 20

अतः परिवारों का बहुलक मासिक व्यय = ₹ 1847.83
तथा माध्य मासिक व्यय = ₹ 2662.50

प्रश्न 4.
निम्नलिखित बंटन भारत के उच्चतर माध्यमिक स्कूलों में, राज्यों के अनुसार, शिक्षक-विद्यार्थी अनुपात को दर्शाता है। इन आँकड़ों के बहुलक और माध्य ज्ञात कीजिए। दोनों मापकों की व्याख्या कीजिए।

प्रति शिक्षक विद्यार्थियों की संख्या	राज्य / संघीय क्षेत्रों की संख्या
15-20 20-25 25-30 30-35 35-40 40-45 45-50 50-55	3 8 9 10 3 0 0 2

हल :
बहुलक के लिए :
यहाँ, अधिकतम बारम्बारता 10 है। इस बारम्बारता का संगत वर्ग अन्तराल 30-35 है।
∴ बहुलक वर्ग = 30-35
∴ l = 30, f₁ = 10, f₀ = 9, f₂ = 3 और h = 5

माध्य के लिए :

माना कल्पित माध्य (A) = 27.5 है।

अतः बहुलक 30.6 तथा माध्य = 29.2, अधिकांश राज्यों / UT. में छात्र और अध्यापक का अनुपात 30.6 और औसतन अनुपात 29.2 है।

प्रश्न 5.
दिया हुआ बंटन विश्व के कुछ श्रेष्ठतम बल्लेबाजों द्वारा एक दिवसीय अन्तर्राष्ट्रीय क्रिकेट मैचों में बनाए गए रनों को दर्शाता है:

बनाए गए रन	बल्लेबाजों की संख्या
3000-4000 4000-5000 5000-6000 6000-7000 7000-8000 8000-9000 9000-10000 10000-11000	4 18 9 7 6 3 1 1

इन आंकड़ों का बहुलक ज्ञात कीजिए।
हल :
बहुलक के लिए दिए गए आँकड़ों में अधिकतम बारम्बारता 18 है। इसका संगत वर्ग अन्तराल 4000 – 5000 है।
∴ बहुलक वर्ग = 4000 – 5000
∴ l = 4000; f₁ = 18; f₀ = 4; f₂ = 9 और h = 1000

अतः दिए गए आँकड़ों का बहुलक = 46087 रन

प्रश्न 6.
एक विद्यार्थी ने एक सड़क के किसी स्थान से होकर जाती हुई कारों की संख्याएँ नोट कीं और उन्हें नीचे दी हुई सारणी के रूप में व्यक्त किया। सारणी में दिया प्रत्येक प्रेक्षण 3 मिनट के अन्तराल में उस स्थान से होकर जाने वाली कारों की संख्याओं से सम्बन्धित है। ऐसे 100 अन्तरालों पर प्रेक्षण लिए गए। इन आँकड़ों का बहुलक ज्ञात कीजिए ।

हल :
दिए गए आँकड़ों में अधिकतम बारम्बारता 20 है। इस बारम्बारता का संगत वर्ग अन्तराल 40-50 है।
∴ बहुलक वर्ग = 40-50
∴ l = 40; f₁ = 20; f₀ = 12; f₂ = 11 और h = 10

अतः दिए गए आँकड़ों का बहुलक 44.7 कारें

Students must go through these JAC Class 10 Science Notes Chapter 8 How do Organisms Reproduce? to get a clear insight into all the important concepts.

JAC Board Class 10 Science Notes Chapter 8 How do Organisms Reproduce?

→ Reproduction: A process by which an organism produces new organism of its own kind is known as reproduction.

• Reproduction unlike other life processes, is not necessary to maintain the life of an individual organism.
  Reproduction involves creation of a DNA copy.
• Variations formed during reproduction are the basis for evolution.
• Reproduction is linked to the stability of population of species.
• Variation is useful for the survival of species over time.

→ Asexual Reproduction : When a single parent is involved in the formation of new generations, without the fusion of gametes it is called asexual reproduction.
Types of Asexual Reproduction :

• Fission
• Budding (e.g., Hydra)
• Spore formation (e.g., Rhizopus)
• Regeneration (e.g., Planaria)
• Fragmentation (e.g., Spirogyra)
• Vegetative propagation.

→ Fission :

• Binary fission (e.g., Amoeba, Leishmania) and
• Multiple fission (e.g., Plasmodium).

→ Vegetative Propagation :

• Natural vegetative propagation and
• Artificial vegetative propagation.

→ Natural vegetative propagation example the adventitious buds developing from the tuberous roots of sweet potato, leaf margins of bryophvllum and normal buds (eyes) on the surface of potato tuber.

• Cutting
• Layering
• Grafting, etc., are the artificial methods for vegetative propagation.

→ Advantage of vegetative propagation : All the plants produced are genetically similar to the parent plant.

→ Sexual Reproduction : A mode of reproduction in which both sexes, male and female are involved to produce new generations is known as sexual reproduction.

Germ cells have half the number of chromosome and half the amount of DNA due to meiosis. When both male and female gamete are fused, there is reestablishment of the number of chromosomes and the DNA content in the new generation. This may be similar to their parents or may be recombined to some extent.

→ Sexual reproduction in flowering plant: Flower is the sexual reproductive organ of flowering plants. The stamen is male reproductive part and the carpel is female reproductive part in flower.

• Pollen grains are produced within the anther of stamen. Male gametes are produced within the pollen grain.
• Female gametes are produced within the ovule of ovary of carpel.
• Fertilised ovule is transformed into seed while fertilised ovary forms the fruit.
• The seed germinates to produce new plant (offspring).

→ Sexual reproduction in human:

• Boys generally attain puberty at the age of 13-14 years and girls attain it at the age of 10-12 years.
• Male gonad – testis, produces sperms as well as sex hormone – testosterone.
• Female gonad – ovary, produces ova as well as sex hormones – estrogen and progesterone.

Sex hormones are responsible for attaining sexual maturity.

→ Male reproductive system in human beings : A pair of testis, vasa deferentia, seminal vesicles, prostate gland, urethra, bulbourethral glands or cowper’s glands and penis. Male reproductive cells, i.e., sperms are tiny bodies that consist mainly of genetic material and a long tail.

→ Female reproductive system in human beings: A pair of ovary, a pair of oviduct (fallopian tubes), uterus, cervix and vagina.

• Female reproductive cell, i.e., egg cell/ovum is large and contains the nutrients.
• If the fertilisation does not occur, then the thick wall of uterus (endometrium) breaks down. The thick wall of uterus along with the blood vessels and dead ovum comes out through vaginal opening in the form of a bleeding known as menstruation. Menstruation lasts for 2 to 8 days.

→ Contraceptive methods used for the control of population :

• Mechanical barriers of contraception : The loop or the copper-T are used in females and condom for males.
• Chemical barriers of contraception : Oral pills for females. By changing the hormonal balance of the body, eggs are not released.
• Surgical methods : Vasectomy, i.e., vas deferens in male is blocked or tubectomy, i.e., fallopian tubes in female is blocked surgically. In both cases fertilisation will not take place.

Students must go through these JAC Class 10 Science Notes Chapter 5 Periodic Classification of Elements to get a clear insight into all the important concepts.

JAC Board Class 10 Science Notes Chapter 5 Periodic Classification of Elements

→ There are 118 elements which are known at present and out of these, 98 elements are naturally occurring.

→ The classification of elements is made on the basis of similarity of their properties.

→ Dobereiner, Newlands, Mandeleev, Lothar Meyer and Henry Moseley made attempt of the classification of elements.

→ Dobereiner’s triads When he observed that three elements were arranged in the order of their increasing atomic masses, the atomic mass of the middle element was roughly the average of the atomic masses of the other two elements. These groups of three elements are called triads.

→ Newlands’ law of octaves When elements are arranged in the order of their increasing atomic masses, the every eighth element (starting from a given element) had properties similar to that of the first element.

→ Mendeleev’s periodic law: The properties of elements are the periodic function of their atomic masses.

→ Mendeleev classified the elements in increasing order of their masses in –

• vertical columns called groups and,
• horizontal rows called periods.

→ Mandeleev named scandium, gallium and germanium as Eka-boron, Eka-aluminium and Eka-silicon respectively.

→ Isotopes : Atoms of the same element having same atomic number but different atomic masses are known as isotopes of each other.

→ Henry Moseley showed that the atomic number of an element is a more fundamental property than its atomic mass.

→ The modem periodic law: The properties of elements are a periodic function of their atomic number.

→ Elements in the modern periodic table are arranged in 18 vertical columns called groups and 7 horizontal rows called periods.

Period number	Number of elements
1	2
2	8
3	8
4	18
5	18
6	32
7	Incomplete period

→ The position of an element in the periodic table provides information to predict its chemical properties and reactivity.

→ Periodic properties : Properties of the elements which are periodic function of their electronic configuration and are repeated after definite interval of atomic numbers.

→ Valency: The valency of an element is determined by the number of valence electrons present in the outermost shell of its atom.
OR
The valency is the combining capacity of an atom of an element to acquire noble gas configuration.

→ In a period, on moving from left to right, the valency of the elements first increases from 1 to 4 and then decreases from 4 to 0, while the valency of all elements in a group remain the same.

→ Atomic size (Atomic radius) : The distance between the centre of the nucleus and the outermost shell of an isolated atom is called atomic size (atomic radius).

→ Trend of atomic radii in a period and in a group The atomic radius decreases on moving from left to right in a period while on moving down in a group, the atomic radius of elements increases.

→ In a periodic table, metallic elements are arranged on left while non-metals are arranged on right and semi-metals or metalloids are arranged in the middle.

→ In the modern periodic table, boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te) and polonium (Po) have intermediate properties between metals and non-metals and hence called metalloids or semi-metals.

→ Metallic elements are electropositive in nature, while non-metals are electronegative in nature.

→ Generally, oxides of non-metals are acidic, while oxides of metals are basic in nature.

→ Atomic number (Z) : The number of protons in the nucleus of an atom of an element is known as the atomic number.

Students must go through these JAC Class 10 Science Notes Chapter 4 Carbon and Its Compounds to get a clear insight into all the important concepts.

JAC Board Class 10 Science Notes Chapter 4 Carbon and Its Compounds

→ All the living structures (plants and animals) are made-up of (or based on) carbon.

→ The earth’s crust contains 0.02 % carbon in the form of minerals.

→ The reactivity of elements is explained as their tendency to attain a completely filled outermost shell, i.e., attains a noble gas configuration.

→ Covalent bond : A chemical bond formed between two or more atoms by mutual sharing of valence electrons is known as a covalent bond.

→ There are three allotropes of carbon:

• Diamond
• Graphite and
• Fullerene

→ Catenation: Carbon has the unique ability to form bonds with other atoms of carbon giving rise to large number of molecules. This property of carbon is called catenation.

→ Compounds of carbon, which are linked by only single bonds between the carbon atoms are called saturated compounds while compounds of carbon having double or triple bonds between the carbon atoms are called unsaturated compounds.

→ Unsaturated organic compounds are more reactive than saturated organic compounds.

→ Structural isomers : The organic compounds having the same molecular formula but different structures are known as structural isomers.

→ Hydrocarbons : The compounds containing carbon and hydrogen only are called hydrocarbons. They may be saturated or unsaturated.

→ Saturated hydrocarbons which contain only single bond between carbon atoms are called alkanes. The unsaturated hydrocarbons which contain one or more double bonds between carbon atoms are called alkenes and those containing one or more triple bonds are called alkynes.

→ Functional group : An atom or a group of atoms which imparts specific properties to the compound is called a functional group. Based on functional group the compounds are classified as alcohol, carboxylic acid, etc.

→ Homologous seeries : A series of organic compounds in succession which differ by a definite group (like – CH₂ -) is called homologous series.
For example,

→ Oxidising agent: Some substances are capable of adding oxygen to other substances, or remove hydrogen are known as oxidising agents. For example, alkaline potassium permanganate, acidified potassium dichromate.

→ Addition reaction : Unsaturated hydrocarbons adds hydrogen in the presence of catalysts such as palladium or nickel to form saturated hydrocarbons. This reaction is known as addition reaction.

→ Substitution reaction: The reaction in which hydrogen atom of saturated hydrocarbon is replaced by functional group is called a substitution reaction.

→ Esterification: A reaction in which a carboxylic acid and an alcohol react in the presence of acid catalyst forming esters and water is known as an esterification reaction.

→ Saponification : The reaction of forming alcohol and sodium salt of carboxylic acid from ester is known as saponification.

→ The action of soaps and detergents are based on the presence of both hydrophobic and hydrophilic groups in the molecule which helps in emulsifying the oily dirt.

Students must go through these JAC Class 10 Science Notes Chapter 3 Metals and Non-metal to get a clear insight into all the important concepts.

JAC Board Class 10 Science Notes Chapter 3 Metals and Non-metal

→ Metals : Metals possesses lustre in their pure state. Metals are hard. It possesses property of malleability and ductility. Metals are good conductors of heat and electricity and their melting points are high. Metals are sonorous.

→ Non-metals: Non-metals are either solids or gases (Exception: Bromine, it is a liquid). They are neither malleable, nor ductile. They are non-conductors of heat and electricity (Exception: Graphite, it is conductor). Their melting points and boiling points are low (Exception : Diamond, it has the highest melting point).

→ Metals combine with oxygen to form metal oxides.

→ Oxides of alkali metals are soluble in water.

→ Metals form basic (For example, Na₂O, MgO) and amphoteric oxides (For example, ZnO, Al₂O₃), while non-metals form acidic and neutral oxides (For example, H₂O, CO, Cl₂O₇).

→ Metals react with acid and water forming hydrogen gas. Non-metals do not release hydrogen gas by reaction with acid and water.

→ When metals reacts with nitric acid, hydrogen gas is not evolved, because nitric acid is a strong oxidising agent.

→ Reactivity series of metals is an arrangement of metals in the descending order of their reactivity. In reactivity series, more reactive metals (elements) are placed at top while less reactive metals (elements) are placed at bottom.

→ A more reactive metal displaces a less reactive metal from its salt solution or from its molten state.

→ Metallurgy The various processes involved in the extraction of metals from their ores in different steps and finally refining the metals.

→ Ionic compounds: The compounds formed by the transfer of electrons from a metal species to a non-metal species forming ions are known as ionic compounds.

→ Properties of ionic compounds : Ionic compounds are brittle. They have high melting point and boiling point. They are soluble in water but insoluble in petrol and kerosene (non-polar solvents). These compounds do not conduct electricity in solid state but they conduct electricity in an aqueous solution or in their molten state.

→ Roasting: The process of strongly heating the sulphide ores in excess of air and converting them into oxides is called roasting.

→ Calcination: The process of strongly heating the carbonate (or hydroxide) ores in a limited supply of air and converting them into metal oxides is called calcination.

→ Alloys: The homogenous mixture of two or more metals or metal and non-metal is called an alloy. For example, brass, bronze, stainless steel, etc.

Students must go through these JAC Class 10 Science Notes Chapter 7 Control and Coordination to get a clear insight into all the important concepts.

JAC Board Class 10 Science Notes Chapter 7 Control and Coordination

→ The movement is shown as a response to a change in the environment by the organism.

→ Each kind of a change in the environment evokes an appropriate movement as a response.

→ Some movements are growth related while others are not.

→ Nervous system and hormones bring about control and coordination of the bodies.

→ Neuron is a structural and functional unit of nervous tissue.

→ Cell body (cyton), dendrites and axon are the structural parts of neuron.

→ The responses of the nervous system can be classified as reflex action, voluntary action and involuntary action.

→ Reflex action is an involuntary response to external stimuli without the knowledge of voluntary centres of brain.

→ Reflex arc is a connection between the input (sensory) nerve and the output (motor) nerve along with spinal cord.

→ Voluntary actions occur under the control of will of an animal.

→ The nervous system uses electrical impulses to transmit messages.

→ Human nervous system :

• Central nervous system is made-up of brain and spinal cord.
• Peripheral nervous system is made-up of cranial nerves and spinal nerves.

Brain has three major parts:

• Fore-brain
• mid-brain and
• hind-brain.

→ Brain is protected in bony box and spinal cord is protected in a vertebral column.

→ The simplest form of movement at the cellular level is the movement of muscle cell.

→ Plants have neither a nervous system nor muscles.

→ Plants show two different types of movements – one dependent on growth and other independent of growth.

→ Touch-me-not is a plant of the Mimosa family whose leaves move very quickly in response to touch.

→ Tendrils of a pea plant are sensitive to touch.

→ Environmental factors such as light, gravity, water, etc. change the directions of growing part of a plant. These are called directional or tropic movements.

→ Chemical coordination is seen in both plants and animals.

→ Auxin, gibberellin and cytokinin are growth promoting hormones of plants. Abscisic acid is a plant hormone which inhibits growth.

→ In animals the chemical coordination is due to neurotransmitters and hormones.

→ An endocrine gland is the ductless gland that secretes hormones.

→ Hormones are directly poured into blood and are transported to their functional site.

→ Pituitary gland, pineal gland, thyroid gland, parathyroid gland, thymus gland, adrenal gland, pancreas and testis or ovary are endocrine glands in human body.

→ The timing and amount of hormone secretion are regulated by feedback mechanisms.

Jharkhand Board JAC Class 10 Science Important Questions Chapter 7 Control and Coordination Important Questions and Answers.

JAC Board Class 10 Science Important Questions Chapter 7 Control and Coordination

Additional Questions and Answers

Question 1.
Distinguish between :
(1) Response in Plants and Response in Animals
Answer:

Response in Plants	Response in Animals
1. Plants do not possess nervous system but only possess hormones for expressing their response.	1. Animals possess both, the nervous system and endocrine system for expressing their response.
2. The response in plants is not rapid and needs more time to be observed.	2. The response in animals is rapid and seen immediately.
3. The response in plants is limited.	3. The response in animals is not limited.
4. There are no muscular tissues in plants to show the response.	4. There are muscular tissues in animals through which the response is shown.
5. In plants, there is no specific tissue for the transmission of information to different parts of the body.	5. In animals there is specific nervous tissue for the transmission of information to different parts of the body.

(2) Nervous System and Endocrinal System
Answer:

Nervous System	Endocrinal System
1. Its structural and functional unit is a neuron (nerve cell).	1. Its functional unit is a hormone.
2. In human body it comprises central nervous system, peripheral nervous system and autonomous nervous system.	2. In human body it comprises of various endocrine glands.
3. Its function is to collect the information, its analysis and interpretation and convey the responsive message to the motor organs.	3. Its function is to produce stimulatory or inhibitory effect on the tissues or organs through the medium of hormones.
4. The coordination that occurs through the nervous system is very rapid as the impulses pass through the nerve fibres.	4. The coordination that occurs through the endocrine system is a relatively slow process as the hormone flows through the blood stream to reach the target organ.

(3) Cerebrum and Cerebellum
Answer:

Cerebrum	Cerebellum
1. It is a major part of the fore-brain.	1. It is a part of the hind-brain.
2. It coordinates thoughts and various other senses.	2. It coordinates the functions of voluntary muscles and thereby maintains the body equilibrium.
3. It is the largest and most complex part of the brain.	3. It is a part lying behind the cerebrum, on the dorsal side beneath the pons.

(4) Plant hormones and Animal hormones
Answer:

Plant hormones	Animal hormones
1. Plant hormones are secreted by plant cells but no specific glands are there.	1. Animal hormones are secreted from endocrine glands.
2. Plant hormones are either growth promoting or growth inhibiting.	2. There is no inhibitor hormone for growth in animals.
3. Plant hormones reach to their target site by simple diffusion.	3. Animal hormones reach to their target site through blood circulation.
4. Secretion of it is not regulated by feedback mechanism.	4. Secretion of some hormones regulated by feedback mechanism.

Question 2.
Give scientific reasons for the following statements:
(1) Response to stimuli is the characteristic of every living organism.
Answer:
All living organisms experience the effects of changes in the atmosphere that surrounds them and tend to respond differently against them.

The living organisms show a slow or rapid response to stimuli such as heat, cold, sound, touch, pressure, etc. Responses are expressed against these stimuli through hormones in plants and nervous system as well as hormones in animals, e.g., The plants bend in the direction of light. Man shows shivering effect in severe cold and perspiration in hot season.

Thus, the response to stimuli is the characteristic of every living organisms.

(2) Unlike animals, the plants do not show immediate response.
Answer:
All organisms show response to stimuli. However, the animals possess nervous system and s sense organs, which are absent in plants. Animals use the nervous system as well as endocrine system for control and coordination of all their activities, while the plants possess only hormones to coordinate their activities. The hormones diffuse from cell to cell quite slowly in plants while most animals have blood for rapid transport of hormones. Because of all these reasons, the plants do not show immediate response.

(3) The roots in plants grow against the direction of light.
Answer:
The roots in plants show positive tropic movement in the direction of water and gravitational force, i.e., The roots show positive hydrotropism and positive geotropism.

Thus, the roots bend in the direction Thus, the roots bend in the direction of water and gravitational force. So it grows against the direction of light.

(4) The central nervous system is very well protected.
Answer:
The central nervous system comprises of a brain and a spinal cord.

Brain is contained in a fluid-filled balloon which absorbs mechanical shocks and thereby protect it from any severe injuries. Moreover, the brain is enclosed in a strong bony box – the cranium of the skull and the spinal cord is enclosed in a long and strong bony vertebral column. Thus, the central nervous system (of the human) is very well protected.

(5) The foot is very suddenly lifted off as soon as it comes in contact with a burning coal.
Answer:
It is a reflex action – In this phenomenon, the impulse commencing from the sensory organ (the skin of the foot) enters into the spinal cord through the sensory nerve fibres. The impulse is analysed in the spinal cord and the responsive motor impulse is transmitted through the motor nerve fibres to the effector organ (the foot muscles) to contract and thereby show the response. Sp the foot is very suddenly lifted off as soon as it comes in contact with a burning coal.

(6) The hormones secreted from the endocrine glands are present everywhere in the body.
Answer:
The hormones are secreted from the endocrine glands which are ductless glands. These glands are richly supplied with blood. The secretions are directly poured in the blood stream. As the blood circulates in all the parts of the body, these hormones are carried and hence present everywhere in the body.

(7) The diabetic patient is given injections of insulin.
Answer:
It is necessary to maintain a definite blood sugar level in the human body. In the patients of diabetes the blood sugar level remains high due to the deficiency of insulin hormone from the pancreas. This higher blood sugar level causes several harmful effects.

To prevent the diabetic patient from such harmful effects the blood sugar level is required to be maintained at certain definite level. Insulin is a hormone that reduces blood sugar level. Hence, the diabetic patient is given injections of insulin.

(8) It is advisable to take iodized salt in daily food.
Answer:
The hormone thyroxin is secreted from the thyroid gland. It is an iodized hormone (rich in iodine). Thyroxin is not formed when there is deficiency of iodine in the blood. As a result, the condition called hypothyrodism occurs in which the size of the thyroid gland gets gradually enlarged, this disease is called goitre. The iodized table salt provides proper amount of iodine for the formation of thyroxin in the thyroid gland.

Hence, it is advisable to take iodized salt in daily food.

Question 3.
Carefully observe the given diagram id answer the questions related with it:

Questions :

1. Identify ‘a’ and state the function of it.
2. At which region in diagram chemicals are released?
3. Identify ‘c’ and state from which it originates.

Answer:

1. a – Dendrite.
   Function: Information received at the end of its tip.
2. At d – region (nerve ending) in diagram chemicals are released.
3. c – Axon. It originates from cell body.

Questions :

1. Identify ‘a and state its function.
2. Where is information stored in brain? Mention its alphabet.
3. State any two functions of part ‘d’
4. Identify ‘c’ State the name of special structure formed by it which show quick response.

Answer:

1. a-Cranium (bony box).
   Function : It protects brain.
2. b – Cerebrum
3. d – Cerebellum. It is responsible for precision of voluntary actions and maintaining the posture and balance of the body.
4. c – Spinal cord. For quick response, the reflex arc is formed by it.

Questions:
(1) State the name of ‘a’ and ‘b’ with location.
(2) State any two functions of ‘b’
(3) In which condition, ‘a’ is stimulated and give the name of its secretion.
Answer:
(1)

Name	Location
a. Adrenal gland	At the anterior of kidneys
b. Pancreas	Under the stomach in abdomen

(2) Functions of ‘b’ (Pancreas) : Secretes insulin and regulates blood sugar level. Secretes pancreatic juice and help in digestion.

(3) In a fear or tense condition ‘a’ (adrenal gland) is stimulated and secretes adrenaline hormone.

Objective Questions and Answers

Question 1.
Answer the following questions in short:
(1) Name the two systems of control and coordination in higher animals.
Answer:
The nervous system and the endocrine system are the two systems of control and coordination in higher animals.

(2) Name the three components of a nerve cell.
Answer:
The three components of a nerve cell s are a cyton, an axon and one or more dendrons.

(3) Name the most important part of the s human brain.
Answer:
The most important part of the human brain is cerebrum which is the largest part of the brain.

(4) State one function of cerebellum.
Answer:

Part	Function
Cerebellum	Coordination of movement of the and maintenance of body equilibrium.

(5) Give the function of medulla.
Answer:
Function of medulla: It maintains the rhythm of various involuntary processess such as breathing, heartbeats, peristalsis of the alimentary s canal, etc.

(6) Name the structural and functional unit of nervous system.
Answer:
The neuron (nerve cell) is the structural and functional unit of nervous system.

(7) Name one hormone secreted by the pituitary gland.
Answer:
One of the hormones secreted by the pituitary gland is GH (Growth Hormone).

(8) Give example of the movement of a plant part which is caused by the loss of water.
Answer:
Sensitive plant: Touch-me-not (Mimosa ( pudica).

(9) What is the response of roots to gravity? What is this phenomenon known as?
Answer:
A root give positive response to gravity, this phenomenon is called positive geotropism.

(10) What is the response of stem to light? What is this phenomenon known as?
Answer:
A stem moves towards light. This phenomenon is known as positive phototropism.

(11) What is an impulse?
Answer:
Information that is transmitted through the nerves in form of electro-chemical signals are called impulse.

(12) What is gustatory receptors? Where they located?
Answer:
The receptors which detect taste are called gustatory receptors. They are located on the surface of tongue.

(13) By what is nervous tissue made-up of? What is its special ability?
Answer:
The nervous tissue is made-up of an organised network of neurons. It is specialised for conducting information via electrical impulses.

(14) State any two examples of movement in order to protect ourselves.
Answer:
When bright light is focussed on eyes, we constrict pupils, we pull our hand when we touch a hot object. These are the examples of movement in order to protect ourselves.

(15) What are components of peripheral nervous system?
Answer:
The peripheral nervous system consists of cranial nerves arising from brain and spinal nerves arising from the spinal cord.

(16) Which separate areas are there in fore brain?
Answer:
There are separate areas specialised for hearing, smell, sight, etc. in fore-brain.

(17) Why thinking is called a complex activity?
Answer:
Thinking is called a complex activity, because it is bound to involve a complicated interaction of many nerve impulses from many, neurons.

(18) How do we know that we have eaten enough?
Answer:
The sensation of feeling full is because of a centre that is associated with hunger, located in separate part of the fore-brain.

(19) Which involuntary actions are controlled by medulla in the hind-brain?
Answer:
Involuntary actions such as blood pressure, salivation, vomiting are controlled by medulla in the hind-brain.

(20) How do animal muscles move?
Answer:
When a nerve impulse reaches the muscle, the muscle fibre can move due to stimulation.

(21) How does a muscle cell move?
Answer:
Muscle cells move by changing their shape either shortening or elongating.

(22) How do muscle cells change their shape?
Answer:
Muscle cells have special proteins that change both their shape and arrangement in cells, so muscle cells change their shape.

(23) How does leaves of chhui-mui respond to touch stimulus?
Answer:
The leaves of the sensitive plant chhui- mui move very quickly in response to touch stimulus.

(24) Why are hormones called chemical messengers?
Answer:
Hormones are called chemical messengers because they carry information in the form of chemicals that regulate the biological processes of body.

(25) Which plant hormone inhibits growth? State its effect.
Answer:
Abscisic acid – a plant hormone that inhibits growth. It affects wilting of leaves.

(26) Why is chemical signal required along with electrical impulses in higher animals?
Answer:
In higher animals, electrical impulses bring immediate response to only those cells that are connected by nervous tissue while chemical signals reaching to each and every cells of body.

(27) Who constitutes a second way of control and coordination in our body?
Answer:
Hormones, secreted by endocrine system constitute a second way of control and coordination in our body.

(28) Where is auxin synthesised and where does it diffuses?
Answer:
Auxin is synthesised at the shoot tip and it diffuses towards the side of the shoot which is in shade.

(29) Secretion of which hormone in males and in females is responsible for pubertal changes?
Answer:
Secretion of testosterone in males and estrogen in females causes changes associated with puberty.

(30) State the secretory site and function of growth hormone releasing factor.
Answer:
Growth hormone releasing factor : Secretory site : Hypothalamus.
Function: Stimulates the pituitary gland to release growth hormone.

Question 2.
Define : OR Explain the terms :
(1) Stimulus
Answer:
The changes, that take place in the external environment of living organisms (plants, animals, microorganisms, etc.) and induce definite types of reactions or responses, are called stimuli (singular – stimulus).

(2) Response
Answer:
The reaction of living organisms against the stimulus induced by the change in the external environment is called response.

(3) Coordination
Answer:
Different organs of the body jointly s function systematically against the stimuli and react to express proper response against the £ stimuli is called coordination.

(4) Tropism
Answer:
The growth related movement in the plant organs, which are induced as a response ” to directional stimulus is called tropism.

(5) Hormone
Answer:
A chemical messenger, synthesised or secreted in extremely small quantities by endocrine

(6) Endocrine gland
Answer:
The ductless glands that secret hormones c are called endocrine gland.

(7) Receptors
Answer:
The specialised structures that receive stimuli from external environment are called t receptors.

(8) Central Nervous System
Answer:
A controlling and coordinating system of body which consists of brain and spinal cord is called central nervous system.

(9) Reflex arc
Answer:
A connection between the input (sensory) nerve and output (motor) nerve along with spinal cord is called reflex arc.
OR
It is a path of reflex action which consists of receptor, sensory neuron, relay neuron and motor neuron connected to effector organ.

Thus a neural pathway for the sensory and motor messages that pass through the spinal cord forms the reflex arc. A very rapid response is shown through it.

The following example can clarify the meaning of reflex arc:
Suppose by mistake and unknowingly one touches a hot object by one’s hand. One would withdraw the hand all of a sudden without giving a slightest thought. Here the hot object is the source of stimulus.

This stimulus activates the sensory nerve fibre in the hand and carry that impulse to the spinal cord. The sensory centres in the spinal cord receive the stimulus and transmits the response to the motor centre of the spinal cord. This motor message is transmitted through the motor nerve fibre to definite muscles of the hand, which upon contraction, withdraws the hand. The hand or its muscles act as effector organ. This entire neural path from the sensory or receptor organ, to the effector organ is a reflex arc.

(10) Synapse
Answer:
In the arrangement of two consecutive neurons the axon fibre endings of one neuron and s the dendrite endings of the next neuron having a microscopic gap is called synapse.

Question 3.
Fill in the blanks :

1. The plants coordinate their behaviour against the environmental changes by using ………………..
2. The responses of plants are not rapid for want of ………………..
3. ……………….. is a growth-inhibitor hormone of plants.
4. The stem exhibits ……………….. geotropism and ……………….. phototropism.
5. The tendrils of pea plants are the example of ………………..
6. The olfactory receptors will detect ………………..
7. ……………….. have evolved in animals as efficient ways of functioning in the absence of true thought processes.
8. ……………….. part of brain for learning process and part of brain responsible for memory.
9. The cells of sensitive plant change shape by changing the ……………….. in them resulting in swelling or shrinking.
10. Cytokinins promotes ……………….. in plants.
11. ……………….. hormone has the target organ heart.
12. The timing and amount of animal hormone released are regulated by …………………

Answer:

1. hormones
2. nervous system
3. Abscisic acid
4. negative, positive
5. thigmotropism
6. smell
7. Reflex arc
8. Cerebellum, cerebrum
9. amount of water
10. cell division
11. Adrenaline
12. feedback mechanism

Question 4.
State whether the following statements are true or false:

1. Many involuntary actions are controlled by the mid-brain and hind-brain.
2. Brain is never involved in reflex action.
3. The communication between the peripheral nervous system and the other parts of the body is facilitated by the central nervous system.
4. Neuromuscular junction is synapse like gap between nerve ending and muscle fibre.
5. When we have cold, efficiency of olfactory receptors reduces.
6. Nerve cells have special proteins that change their shape and arrangement for conduction of impulse.
7. Touch-me-not, a sensitive plant is of the Mimosa family.
8. The movement of sunflowers in response to day or night is quite fast.
9. The sensitive plants detect the touch though there is no nervous tissue or any muscle tissue.
10. Gibberellin gives signal to plant to stop the growth.
11. Hypothalamus plays an important role in the release of many hormones from pituitary gland.
12. Chemical coordination is seen in both plants and animals.

Answer:

1. True
2. False
3. False
4. True
5. True
6. False
7. True
8. False
9. True
10. False
11. True
12. True

Question 5.
Match the following:
(1)

Column I	Column II
1. Fore-brain	a. Balance of body
2. Medulla	b. Reflex arc
3. Cerebellum	c. Main thinking part
4. Spinal cord	d. Salivation

Answer:
(1 → c), (2 → d), (3 → a), (4 → b).

(2)

Column I	Column II
1. Insulin	a. Testes
2. Testosterone	b. Pancreas
3. Growth hormone	c. Ovaries
4. Estrogen	d. Pituitary

Answer:
(1 → b), (2 → a), (3 → d), (4 → c).

(3)

Column I	Column II
1. Auxin	a. Wilting of leaves
2. Gibber ellin	b. Promotes cell-division
3. Cytokinin	c. Helps in stem-growth
4. Abscisic acid	d. Phototropism

Answer:
(1 → d), (2 → c), (3 → b), (4 → a).

(4)

Column I	Column II
1. Adrenaline	a. Regulates blood sugar level
2. Thyroxin	b. Increases breathing, heart beats.
3. Insulin	c. Regulates menstrual cycle.
4. Estrogen	d. Regulates metabolism for body growth.

Answer:
(1 → b), (2 → d), (3 → a), (4 → c).

Question 6.
Chart-diagram based questions:
1. Which of the following diagram is correct? Why?
Answer:

Diagram (a) is correct, because roots show positive geotropism and stem shows negative geotropism.

2. Label (a), (b), (c) and (d) in the given figure showing the pathway of thermal impulse.

Answer:
(a) Sensory neuron
(b) Relay neuron
(c) Motor neuron
(d) Effector = muscle in skin

3. Identify (a), (b), (c) and (d) in the given figure. Give one name of the hormone secreted I; from each of any two of them.

Answer:
(a) Pineal gland – Melatonin hormone
(b) Pituitary gland – Growth hormone
(c) Thyroid gland – Thyroxine
(d) Thymus gland – Thymocine

4. A graph shows change after a lunch of a healthy individual whose diet is rich in sweets.

What you explain from it?
Answer:
When the sugar level rises in blood, pancreas releases more insulin to regulate blood sugar level. As blood sugar level falls, insulin secretion is reduced by feedback mechanism.

Question 7.
Select the correct alternative from those given below each question:
1. The roots of a plant are ………………..
A. positive phototropic, but negative geotropic
B. negative geotropic, but negative phototropic
C. negative phototropic, but positive hydrotropic
D. negative hydrotropic, but positive phototropic
Answer:
C. negative phototropic, but positive hydrotropic

2. The diagram shows a plant which has received light from one side only. Which characteristics are shown by the plant?

A. Excretion and growth
B. Response and reproduction
C. Growth and response
D. Reproduction and nutrition
Answer:
C. Growth and response

3. The growth of a pollen tube towards the ovule is caused by
A. phototropism
B. hydrotropism
C. geotropism
D. chemotropism
Answer:
D. chemotropism

4. For the synthesis of which of the following hormone is iodine necessary?
A. Adrenaline
B. Auxin
C. Thyroxin
D. Insulin
Answer:
C. Thyroxin

5. Which of the following hormone prepares our body for action in emergency situations?
A. Testosterone
B. Growth hormone
C. Adrenaline
D. Insulin
Answer:
C. Adrenaline

6. Which is male sex hormone?
A. Estrogen
B. Adrenaline
C. Testosterone
D. Progesterone
Answer:
C. Testosterone

7. Which of the following endocrine gland does not occur as a pair in the human body?
A. Adrenal
B. Pituitary
C. Testis
D. Ovary
Answer:
B. Pituitary

8. Which of the following helps in maintaining posture and balance of the human body?
A. Cerebrum
B. Cerebellum
C. Medulla
D. Pons
Answer:
B. Cerebellum

9. Which of the following plant shows immediate response to touch by its leaves?
A. Sunflower
B. Pea
C. Mimosa
D. None of the given
Answer:
C. Mimosa

10. By whom are the continuous heartbeats controlled?
OR
Where are the regulatory centres for the blood pressure located?
A. Cerebrum
B. Cerebellum
C. Mid-brain
D. Medulla
Answer:
D. Medulla

11. Which of the following plant hormone helps in the growth of the stem?
A. Auxin
B. Gibberellin
C. Cytokinin
D. Abscisic acid
Answer:
A. Auxin, Gibberellin

12. Through whom does the impulse enter into the cyton?
A. Dendrite
B. Axons
C. Both A and B
D. None of the given
Answer:
A. Dendrite

13. Which is the largest and the most complex part of the human brain?
A. Medulla
B. Cerebellum
C. Hypothalamus
D. Cerebrum
Answer:
B. Cerebellum

14. Who regulates the involuntary reflexes such as coughing, sneezing, hickup, vomiting, etc.?
A. Medulla
B. Cerebellum
C. Hypothalamus
D. Cerebrum
Answer:
A. Medulla

15. The deficiency of which hormone causes diabetes?
A. Estrogen
B. Thyroxin
C. Adrenaline
D. Insulin
Answer:
D. Insulin

16. Where is the arrangement in the body for i reflex action?
A. In medulla oblongata
B. In spinal cord
C. In pons
D. In heart
Answer:
B. In spinal cord

17. What is the main function of endocrine system in animals?
A. Coordination
B. Combination
C. Regulatory
D. None of the given
Answer:
A. Coordination

18. Which ovarian hormone regulates menstrual cycle in women?
A. Testosteron
B. Estrogen
C. Thyroxin
D. None of these
Answer:
B. Estrogen

19. Which gland is stimulated to release its <; secretion in a scary situation in squirrels?
A. Adrenal
B. Pituitary
C. Thyroid
D. Hypothalamus
Answer:
A. Adrenal

20. “Withdrawal of hand when unknowingly rose prickle pricks the hand”, which is this process?
A. Autonomous reaction
B. Reflex action
C. Thigmotropism
D. None of the given
Answer:
B. Reflex action

21. Hypothalamus is a part of ……………..
A. Fore-brain
B. Spinal cord
C. Muscle tissue
D. Cerebellum
Answer:
A. Fore-brain

22. Who secretes releasing hormones?
A. Pituitary gland
B. Hypothalamus
C. Autonomous Nervous System
D. Thalamus
Answer:
B. Hypothalamus

23. Whose excessive secretion causes the body to look like a gorilla?
A. Thyroxin
B. Growth hormone
C. Adrenaline
D. All of the given
Answer:
B. Growth hormone

24. Which disease takes place when there is a increase of sugar in the blood and in the mine?
A. Dwarfism
B. Goitre
C. Diabetes
D. Both A and B
Answer:
C. Diabetes

25. Statement A: Adrenaline diverts the blood to skeletal muscles of squirrel.
Reason R: Squirrel relies not only on electrical impulses but also on chemical signals.
Which option is correct for Statement A and Reason R?
A. Both A and R are correct and R is explanation of A.
B. Both A and R are correct, but R is not explanation of A.
C. A is correct, R is incorrect.
D. A is incorrect, R is correct.
Answer:
B. Both A and R are correct, but R is not explanation of A.

26. Statement A: The fore-brain is the main thinking part of the brain.
Reason R: Thinking is a complex activity that S involves a complicated interaction? of many nerve impulses.
Which option is correct for Statement A and i Reason R?
A. Both A and R are correct and R is explanation of A.?
B. Both A and R are correct, but R is not explanation of A.
C. A is correct, R is incorrect.
D. A is incorrect, R is correct.
Answer:
A. Both A and R are correct and R is explanation of A.?

27. Statement A: Auxin helps the cells to grow longer and plant appears to bend s towards light.
Reason R: Auxin diffuses towards shady side s of shoot from its tip.
Which option is correct for Statement A and Reason R?
A. Both A and R are correct and R is explanation of A.
B. Both A and R are correct, but R is not? explanation of A.
C. A is correct, R is incorrect.
D. A is incorrect, R is correct.
Answer:
A. Both A and R are correct and R is explanation of A.

28. How many endocrine glands from following are not in pairs?
Pancreas, adrenal, thyroid, testes, pituitary?
A. 2
B. 3
C. 4
D. 5
Answer:
B. 3

29. Find incorrect statement for cerebrum.?
A. It receives sensory impulses from various receptors.
B. It has areas where information stored.
C. It passes information to motor areas which control the movement of voluntary muscles.?
D. It maintains posture and balance of the body.
Answer:
D. It maintains posture and balance of the body.

30. Which is sensitive to touch?
A. Human skin
B. Tendrils of pea
C. Leaves of mimosa
D. Flowers of Sunflower?
Answer:
A. Human skin, Tendrils of pea, Leaves of mimosa

Question 8.
Answer as directed : (Miscellaneous)
(1) What is full form of CNS?
Answer:
CNS – Central Nervous System

(2) Give the correct sequence of conduction of impulse.
Answer:
Correct sequence of conduction of impulse : Dendrite → cell body → axon → nerve ending → synapse → dendrite

(3) Trace the sequence of events which occur when a bright light is focused on your eyes?
Answer:
Stimulus (bright light) → photo receptors of eyes
↓
pupil ← motor ← mid – ← sensory nerves constrict nerve brain /neurons (neuron)

(4) Find mismatched pair :
(i) Iodine – Functioning of thyroid gland
(ii) Insulin – Regulates blood sugar level
(iii) Hypothalamus – Regulates the secretion of pituitary
(iv) Estrogen-Obstructs menstrual cycle
Answer:
(iv) Estrogen-Obstructs menstrual cycle

(5) Identify me : I am a hormone generally for an emergency, increases breathing rate but reduce blood flow to digestive system and skin.
Answer:
Adrenaline

(6) State the correct sequence of impulse for spinal reflex.
Answer:
Receptors in skin → sensory neuron → spinal cord motor neuron effector (muscles)

(7) Who am I? I am present in greater concentration areas of rapid cell division, such as in fruits and seeds.
Answer:
Cytokinin

(8 ) Movement dependent on growth : Tendrils of pea :: Movement independent of growth : ………………
Answer:
Drooping of leaves of chhui-mui

(9) Which event is indicated in the diagram? Which hormone is responsible for it?

Answer:
Positive phototropism in shoot is indicated in the diagram. Auxin is responsible for it.

(10) Deficiency of growth hormone: ……………… ::
Deficiency of ……………… : diabetes
Answer:
Dwarfism, Insulin

(11) Identify me : I am controlling your daily activities such as walking, riding a bicycle, picking up object, etc.
Answer:
Cerebellum

(12) Find mismatched pair:
(i) Growth related movement – slower
(ii) Movement in sunflower in response to day or night – quite slow
(iii) Movement of our leg-very slow
Answer:
(iii) Movement of our leg-very slow

(13) Give the scientific terms used to represent the following:
(i) Bending of a shoot towards light
Answer:
Phototropism

(ii) Growing of roots towards the earth
Answer:
Geotropism

(iii) Growing of a pollen tube towards ovule
Answer:
Chemotropism

(iv) Bending of roots towards water
Answer:
Hydrotropism

(v) Winding of tendril around a support
Answer:
Thigmotropism

(14) Bony box : Brain
……………… : Spinal cord
Answer:
Backbone (vertebral column)

Fill a and b to make the correct sequence.
Answer:
a – growth hormone releasing factor
b – pituitary gland

Value Based Questions With Answers

Question 1.
You saw a tragic road accident resulting in death of two persons. The reason for that is bike rider tried to overtake the truck from wrong-side with overspeed. He was not wearing a helmet that caused head injury.

You were scared because you also have same habit to drive activa without wearing helmet. Your father often warned you that to drive vehicle without a driving licence is a crime.
Questions :

1. Which part of brain is involved into learning how to drive vehicle?
2. Injury to which part of brain leads to instant death of an individual? Why?
3. Which gland became more active when you saw the accident? Which hormone was poured in blood? What changes did you feel in body?

Answer:

1. Cerebrum and Cerebellum
2. Medulla oblongata. Because all involuntary activities are controlled by it. Injury to that part disturbs all involuntary functions and leads to instant death.
3. Adrenal gland became more active. Adrenaline s hormone was poured in blood. Perspiration, increased heartbeats and breathing rate, etc. were the changes felt in the body.

Question 2.
Your father-mother are in a age-group at forty plus. On their routine blood test, some disturbance in their blood tests were reported, s Your family doctor advised your father to walk? regularly and consume a diet containing low s sugar. Doctor insisted your mother to take 25 mg elthroxine tablet daily.

Questions:

1. From your study, what do you think about s the report of the blood test of your father?
2. Which gland is not functioning properly and which hormone is not secreted in s appropriate amount in your father’s body?
3. Which gland is affected in your mother’s? body?
4. Why elthroxine tablet is suggested by the S doctor?

Answer:

1. Blood sugar level may be more than the normal level in the blood of father.
2. Pancreas, insulin
3. Thyroid gland
4. Elthroxine is a synthetic thyroxine. It fulfills? the deficiency of thyroxine.

Question 3.
You were visiting your friend’s house. You observed some indoor plants in drawing room. You noticed that shoots of all plants slightly moved towards open window. Aunty told you that she had often changed the position of s the arrangement of plants. But in any position shoots of plants showed same behaviour.

Questions:

1. Which movements are shown by plants?
2. Which hormone is responsible for such movement in plant?
3. How such hormone is functioning in plant body?
4. Which arrangement do you suggest for plants to show straight growth of shoot?

Answer:

1. Phototropism
2. Auxin
3. Auxin is synthesised at shoot tip and it diffuses towards shady side of the shoot. It stimulates the cells to grow longer on the side of the shoot which is away from light.
4. Generally plants that are arranged in open area where they get direct sunlight, may grow straight shoots.

Question 4.
Note five different situations you have experienced in which your adrenal gland had become overactive and had given you a ‘fight or rim away’ response.

The situations in which your adrenal gland had become overactive and had given a ‘fight or run away’ response.
(1) While driving an autovehicle without having a license, the police attempted to stop your vehicle and you increased your speed in an attempt to run away.

(2) Your classteacher caught you telling lie, even though you had not done your homework assigned.

(3) At the annual examination of Std. IX, you felt that the question paper of Science and Technology set at the examination was tough and you were afraid in the examination hall and started perspiring profusely.

(4) You went to see movie in the cinema hall by bunking the school. School authority informed about your absence in the classroom, to your parents. You tried to tell a lie at home and you were caught.

(5) In the World Cup Cricket final match Sehwag and Sachin were out with very low scores and you became tense, thinking that this prestigeous match will be lost.

[Note : In the conditions of stress or fear, there is somewhat over secretion of adrenaline from the adrenal glands.]

Practical Skill Based Questions With Answers

Question 1.
Four different students of your class observed network of neurons in a slide under microscope. They drew a diagram of synaptic junction.
From your knowledge.
Questions:

• Which of the following figures shows the correct pathway for the conduction of impulse?
• What is synaptic junction?
• Which other junction do you know that is some what similar to synapse?
  

Answer:

• Diagram (c) shows correct pathway for the conduction of impulse.
• A microscopic gap between nerve ending of axon of a neuron and dendrites of next neuron is called synaptic junction.
• Neuromuscular junction.

Question 2.
Your subject teacher arranged a potted plant as shown in figure (a). Next day turn its position horizontally as shown in figure (b). After few days, you observed the plant as shown in figure (c).

Questions :

• State the direction of growth of root and stem in the plant.
• What happens when the pot along with the plant is placed as in fig. (b)?
• Why the growth of the entire plant as shown in fig. (b) does not occur parallel to the soil surface?
• Which type of movement does this experiment explain?

Answer:

• The growth of root is negative phototropic and positive geotropic. The growth of stem is positive phototropic.
• When the plant was placed as in fig. (b). both stem and root were initially horizontal.
• The entire plant growth does not occur parallel to the soil surface because stem grows towards light and away from gravity.
• This experiment explains tropic movements due to growth in plant.

Question 3.
Observe figs, (a), (b). (c) and (d).

• Determine on the basis of your observations whether the movement occurring in the plant is growth based or not?
• State the type of movement occurred herein.
  

Answer:
In figures (a), (b) and (c) the movements are’ growth related and in fig. (d) the movement is not related to growth.

Memory Map:

Jharkhand Board JAC Class 10 Maths Important Questions Chapter 4 द्विघात समीकरण Important Questions and Answers.

JAC Board Class 10th Maths Important Questions Chapter 4 द्विघात समीकरण

लयूत्तरात्मक / निबन्धात्मक प्रश्न :

प्रश्न 1.
एक मोटर बोट जिसकी स्थिर जल में चाल 18 किमी / घण्टा है। वह वोट 12 किमी धारा के प्रतिकूल जाने में समय धारा के अनुकूल जाने की अपेक्षा अधिक लेती है। धारा की चाल ज्ञात कीजिए।
हल :
माना कि धारा की चाल x किमी / घण्टा है।
धारा की अनुकूल में मोटर बोट की चाल = (18 + x) किमी / घण्टा
धारा की प्रतिकूल जाने में मोटर बोट की चाल = (18 – x) किमी / घण्टा
धारा की प्रतिकूल में जाने में लगा समय = \(\frac{12}{18-x}\) घण्टे
[∵ समय = दूरी / चाल]
इसी प्रकार अनुकूल जाने में लगा समय = \(\frac{12}{18+x}\) घण्टे
प्रश्नानुसार,
\(\frac{12}{18-x}-\frac{12}{18+x}\) = \(\frac{1}{2}\)
2 × 12 [(18 + x) – (18 – x)] = (18 + x) (18 – x)
24 [18 + x – 18 + x] = 324 – x²
24 × 2x = 324 – x²
48x + x² – 324 = 0
⇒ x² + 48x – 324 = 0
श्रीधराचार्य सूत्र से :
x = \(\frac{-48 \pm \sqrt{48^2+1296}}{2}\)
= \(\frac{-48 \pm \sqrt{3600}}{2}\)
= \(\frac{-48 \pm 60}{2}\)
= 6 या – 54
∵ x धारा की चाल है और यह ऋणात्मक नहीं हो सकती है। इसलिए हम – 54 को छोड़ देते है।
∴ धारा की चाल x = 6 किमी / घण्टा है।

प्रश्न 2.
एक रेलगाड़ी 63 किमी दूरी सामान्य चाल से तथा 72 किमी दूरी सामान्य चाल से 6 किमी / घण्टा ज्यादा चाल से तय करती है। यदि रेलगाड़ी यात्रा को पूरा करने में 3 घण्टे का समय लेती है, तो उसकी सामान्य चाल क्या है ?
हल :
माना कि रेलगाड़ी की चाल x किमी / घण्टा है। तब रेलगाड़ी की बढ़ी हुई चाल = (x + 6) किमी / घण्टा ।

⇒ 45x + 126 = x² + 6x
⇒ x² + 6x – 45x – 126 = 0
⇒ x² – 39x – 126 = 0
⇒ x² – (42 – 3)x – 126 = 0
⇒ x² – 42x + 3x – 126 = 0
⇒ x (x – 42) + 3 (x – 42) = 0
⇒ (x – 42) (x + 3) = 0
यदि x – 42 = 0 हो, तो x = 42
या x + 3 = 0 हो, तो x = – 3
∵ x रेलगाड़ी की सामान्य चाल है तथा यह कभी भी ऋणात्मक नहीं हो सकती है।
∴ x = – 3 को छोड़ देते हैं।
अत: x = 42
इसलिए रेलगाड़ी की सामान्य चाल = 42 किमी/ घण्टा ।

प्रश्न 3.
9000 रुपये को समान रूप से कुछ लोगों में बाँटा गया। यदि 20 व्यक्ति और होते तो प्रत्येक व्यक्ति को 160 रुपये कम मिलते। व्यक्तियों की वास्तविक संख्या कितनी है?
हल :
माना व्यक्तियों की वास्तविक संख्या है।
∴ प्रत्येक व्यक्ति का हिस्सा = \(\frac{9000}{x}\)
यदि व्यक्तियों की संख्या 20 और बढ़ायी जाए तो प्रति व्यक्ति का हिस्सा = \(\frac{9000}{x+20}\)
चूँकि 20 व्यक्ति बढ़ने पर प्रति व्यक्ति का हिस्सा 160 रुपये कम हो जाता हैं ।

⇒ 9000 × 20 = 160x (x + 20)
⇒ x² + 20x – 1125 = 0
⇒ x² + 45x – 25x – 1125 = 0
⇒ x(x + 45) – 25(x + 45) = 0
⇒ (x + 45)(x – 25) = 0
अर्थात् x + 45 = 0 या फिर x – 25 = 0
x = – 45 या x = 25
∵ व्यक्तियों की संख्या ऋणात्मक नहीं हो सकती है।
अतः व्यक्तियों की वास्तविक संख्या = 25 है।

प्रश्न 4.
17 मीटर व्यास वाले एक वृत्ताकार पार्क की परिसीमा के एक बिन्दु पर एक खम्भा इस प्रकार गाड़ना है कि इस पार्क के एक व्यास के दोनों अन्त बिन्दुओं पर बने फाटकों A और B से खम्भे की दूरियों का अन्तर 7 मीटर हो क्या ऐसा करना सम्भव है ? यदि है, तो दोनों फाटकों से कितनी दूरियों पर खम्भा गाड़ना है ?
हल :
माना कि बिन्दु C पर खम्भा गाड़ा गया है तथा फाटक B से बिन्दु C की दूरी = x मीटर

प्रश्नानुसार, फाटक B और A से खम्भे की दूरियों का अन्तर 7 मी. है।
∴ AC = (x + 7) मी.
चूँकि AB व्यास है।
अतः ∠ACB = 90°
(∵ अर्द्धवृत्त में बना कोण समकोण होता है)
अब समकोण त्रिभुज ACB में,
AB² = AC² + BC²
(पाइथागोरस प्रमेय से)
⇒ (17)² = (x + 7)² + x²
⇒ 289 = x² + 49 + 14x + x²
⇒ 289 = 2x² + 14x + 49
⇒ 2x² + 14x + 49 – 289 = 0
⇒ 2x² + 14x – 240 = 0
⇒ x² + 7x – 120 = 0
अब b² – 4ac = (7)² – 4 × 1 × (120)
= 49 + 280
= 529 > 0
अतः दिए गए द्विघात समीकरण के दो वास्तविक मूल है और इसलिए खम्भे को पार्क की परिसीमा पर गाड़ा जा सकता है।
अब x² + 7x – 120 = 0
⇒ x² + (15 – 8)x – 120 = 0
⇒ x² + 15x – 8x – 120 = 0
⇒ (x² + 15x) (8x + 120) = 0
⇒ x(x + 15) – 8 (x + 15) = 0
⇒ (x + 15 ) (x – 8 ) = 0
⇒ x + 15= 0 और x 8 = 0
⇒ x = – 15 और x = 8
∵ x खम्भे और फाटक B के बीच की दूरी है। अतः यह कभी भी ऋणात्मक नहीं हो सकती है।
अतः x = – 12 को छोड़ देते हैं।
अतः x = 8 मी और x + 7 = 8 + 7 = 15 मी
अतः खम्भे से फाटक की दूरी 15 मीटर तथा फाटक B से 8 मीटर है।

प्रश्न 5.
500 किमी की एक हवाई उड़ान में एक वायुयान खराब मौसम के कारण धीनी गति से चला। पूरी उड़ान की औसत चाल 200 किमी / घंटा घट गई तथा उड़ान का समय 30 मिनट बढ़ गया। उड़ान का मूल समय ज्ञात कीजिए ।
हल :
माना वायुयान की सामान्य चाल x किमी / घंटा है।
वायुयान की घटी चाल = (x – 200) किमी / घंटा
दूरी = 600 किमी
600 किमी दूरी तय करने में वायुयान को लगा समय = दूरी / चाल = \(\frac{600}{x}\)घंटे
नई चाल से 600 किमी दूरी तय करने में लगा समय = \(\frac{600}{x-200}\)घंटे
प्रश्नानुसार,

⇒ x² – 200x = 2400
⇒ x² – 200x – 2400 = 0
⇒ x² – 600x + 400x – 2400 = 0
⇒ x(x – 600) + 400(x – 600) = 0
⇒ (x – 600) (x + 400) = 0
यदि x – 600 = 0 तो x = 600
और यदि x + 400 = 0, तो x = – 400
∵ वायुयान की चाल ऋणात्मक नहीं तो सकती, इसलिए x ≠ – 400
∴ वायुयान की सामान्य चाल = 600 किमी / घंटा
अतः उड़ान का मूल समय = दूरी / चाल = \(\frac{600}{600}\) = 1 घंटा

प्रश्न 6.
एक रेलगाड़ी 480 किमी की दूरी एकसमान चाल से चलती है। यदि उसकी चाल 8 किमी / घंटा कम हो, यह उसी दूरी को तय करने में 3 घंटे अधिक लेती है। रेलगाड़ी की मूल चाल ज्ञात कीजिए।
हल :
माना रेलगाड़ी की मूल चाल किमी/घंटा है।
तब रेलगाड़ी की नई घटी हुई चाल (x – 8) किमी / घंटा है।
दूरी = 480 किमी
प्रश्नानुसार,
\(\frac{480}{x-8}-\frac{480}{x}\) = 3
[∵ समय = दूरी / चाल]
⇒ \(\frac{480[x-(x-8)]}{x(x-8)}\) = 3
⇒ 480 × 8 = 3x (x – 8)
⇒ x² – 8x = 1280
⇒ x² – 8x – 1280 = 0
⇒ x² – 40x + 32x – 1280 = 0
⇒ x(x – 40) + 32(x – 40) = 0
⇒ (x – 40) (x + 32) = 0
यदि x – 40 = 0 तो x = 40
और यदि x + 32 = 0 तो x = – 32, जो कि असम्भव हैं, क्योंकि चाल ऋणात्मक नहीं हो सकती।
अतः रेलगाड़ी की मूल चाल 40 किमी/घंटा है।

प्रश्न 7.
एक तेज चलने वाली रेलगाड़ी 600 किमी की यात्रा में एक धीमी चलने वाली रेलगाड़ी से 3 घंटे कम समय लेती है। यदि धीमी चलने वाली रेलगाड़ी की चाल, तेज चलने वाली रेलगाड़ी की चाल से 10 किमी / घंटा कम है, तो दोनों गाड़ी की चाल ज्ञात कीजिए।
हल :
माना तेज चलने वाली रेलगाड़ी की चाल x किमी / घंटा है,
तब
धीमी चलने वाली रेलगाड़ी की चाल (x – 10) किमी / घंटा होगी।
तेज चलने वाली गाड़ी द्वारा 600 किमी की यात्रा में लिया गया समय = \(\frac{600}{x}\) घंटे
धीमी चलने वाली गाड़ी द्वारा 600 किमी. की यात्रा में लिया गया समय = \(\frac{600}{x-10}\) घंटे
प्रश्नानुसार,
\(\frac{600}{x-10}-\frac{600}{x}\) = 3
⇒ \(\frac{600[(x-(x-10)]}{x(x-10)}\) = 3
⇒ 600 × [(x – (x + 10)] = 3x(x – 10)
⇒ 6000 = 3x(x – 10)
⇒ x(x – 10) = 2000
⇒ x² – 10x – 2000 = 0
⇒ x² – 50x + 40x – 2000 = 0
⇒ x (x – 50) + 40 (x – 50) = 0
⇒ (x – 50) (x + 40) = 0
यदि x – 50 = 0, तो x = 50
और यदि x + 40 = 0 तो x = – 40; जो कि असम्भव है।
अत: तेज चलने वाली रेलगाड़ी की चाल = 50 किमी / घंटा
तथा धीमी चलने वाली रेलगाड़ी की चाल = (50 – 10) किमी / घंटा = 40 किमी / घंटा

प्रश्न 8.
दो प्राकृत संख्याओं का अंतर 5 है, तथा उनके प्रतिलोमों का अंतर \(\frac{1}{10}\) है। संख्याएँ ज्ञात कीजिए।
हल :
माना दो प्राकृत संख्याएँ और x + 5 हैं।
प्रश्नानुसार,
⇒ \(\frac{1}{x}-\frac{1}{x+5}\) = \(\frac{1}{10}\)
⇒ \(\frac{(x+5)-x}{x(x+5)}\) = \(\frac{1}{10}\)
⇒ \(\frac{5}{x^2+5 x}\) = \(\frac{1}{10}\)
⇒ x² + 5x = 50
⇒ x² + 5x – 50 =0
⇒ x² + 10x – 5x – 50 = 0
⇒ x(x + 10) – 5(x + 10) = 0
⇒ (x + 10) (x – 5) = 0
यदि x + 100, तो x = – 10; जो कि असम्भव है, क्योंकि कि प्राकृत संख्याएँ ऋणात्मक नहीं होती।
यदि x – 5 = 0, तो x = 5
तथा x + 5 = 5 + 5 = 10
अतः दो प्राकृत संख्याएँ 5 और 10 है।

प्रश्न 9.
एक व्यक्ति के पास एक टूर (यात्रा) के दौरान खर्च के लिए ₹ 4200 हैं। यदि वह अपना दूर 3 दिन बढ़ा दे उसे अपना प्रतिदिन का व्यय ₹70 कम करना पड़ता है। उसके दूर की मूल अवधि ज्ञात कीजिए।
हल :
माना व्यक्ति के टूर की अवधि दिन है।
प्रतिदिन का व्यय = \(\frac{4200}{x}\)
यदि दूर 3 दिन बढ़ा दिया जाए, तब प्रतिदिन का व्यय = \(\frac{4200}{x+3}\)
प्रश्नानुसार,
\(\frac{4200}{x}-\frac{4200}{x+3}\) = 70
⇒ \(\frac{4200[x+3-x]}{x(x+3)}\) = 70
⇒ 4200 × 3 = 70x (x + 3)
⇒ \(\frac{4200 \times 3}{70}\) = x² + 3x
⇒ x² + 3x – 180 = 0
⇒ x + 15x – 12x – 180 = 0
⇒ x(x + 15) – 12 (x + 15) = 0
⇒ (x + 15) (x – 12) = 0
यदि x + 15 = 0, तो x = – 15; जो कि असम्भव है, क्योंकि दिनों की संख्या ऋणात्मक नहीं हो सकती।
और यदि x – 12 = 0, तो x = 12
अतः यात्रा की अवधि 12 दिन है।

प्रश्न 10.
तीन क्रमागत धनपूर्णांक ऐसे हैं कि पहले के वर्ग तथा अन्य दो कि गुणनफल को जोड़ने पर 46 प्राप्त होता है। पूर्णांक ज्ञात कीजिए।
हल :
माना तीन क्रमागत धनपूर्णांक x (x + 1) तथा (x + 2) हैं।
प्रश्नानुसार,
x² + (x + 1)(x + 2) = 46
x² + x + 2x + x + 2 = 46
2x² + 3x + 2 – 46 = 0
2x² + 3x – 44 = 0
2x² + 11x – 8x – 44 = 0
x(2x + 11) – 4(2x + 11) = 0
(2x + 11) (x – 4) = 0
यदि 2x + 11 = 0, तो x = – \(\frac{11}{2}\), असम्भव क्योंकि ऋणात्मक है।
यदि x – 4 = 0, तो x = 4
∴ x + 1 = 4 + 1 = 5 और x + 2 = 4 + 2 = 6
अतः अभीष्ट धनपूर्णांक संख्याएँ 4, 5 और 6 हैं।

प्रश्न 11.
कुछ विद्यार्थियों ने पिकनिक पर जाने की योजना बनाई खाने का कुल बजट ₹ 2000 रखा गया परन्तु 5 विद्यार्थियों के न आने पर प्रति विद्यार्थी खाने पर खर्च ₹ 20 बढ़ गया। कितने विद्यार्थी पिकनिक पर गए तथा प्रत्येक विद्यार्थी ने खाने के लिए कितनी राशि दी ?
हल :
माना पिकनिक पर x विद्यार्थी गए।
कुल धन राशि = ₹ 2000
∴ प्रत्येक विद्यार्थी द्वारा दी गई राशि = \(\frac{2000}{x}\)
यदि 5 विद्यार्थी न आते तब प्रत्येक विद्यार्थी द्वारा दी गई राशि = \(\frac{2000}{x-5}\)
प्रश्नानुसार,
\(\frac{2000}{x-5}-\frac{2000}{x}\) = 20
\(\frac{2000[x-(x-5)]}{x(x-5)}\) = 20
2000 × 5 = 20x (x – 5)
500 = x² – 5x
x² – 5x – 500 = 0
x² – 25x + 20x – 500 = 0
x – (x – 25) + 20(x – 25) = 0
(x – 25) (x + 20) = 0
यदि x – 25 = 0, तो x = 25
और यदि x + 20 = 0 तो x = – 20 (असम्भव)
अतः पिकनिक पर गए विद्यार्थी = 25
प्रत्येक विद्यार्थी द्वारा दी गई राशि = ₹ \(\frac{2000}{25}\) = ₹ 80

प्रश्न 12.
एक ऐसे आयताकार पार्क को बनाना है जिसकी चौड़ाई उसकी लम्बाई से 3 मी कम है। इसका क्षेत्रफल पहले से निर्मित समद्विबाहु त्रिभुजाकार पार्क जिसका आधार आयाताकार पार्क की चौड़ाई के बराबर तथा ऊँचाई 12 मी. है, से 4 वर्ग मी. अधिक हो। इस पार्क की लम्बाई और चौड़ाई ज्ञात कीजिए।
हल :
माना पार्क की लम्बाई x मी है।
पार्क की चौड़ाई (x – 3) मी होगी।
आयताकार पार्क का क्षेत्रफल = x (x – 3) वर्ग मी समद्विबाहु त्रिभुजाकार पार्क का आधार = आयताकार पार्क की चौड़ाई = (x – 3) मी ऊँचाई = 12 मी
समद्विबाहु त्रिभुजाकार पार्क का आधार
= \(\frac{1}{2}\) × आधार × ऊँचाई
= \(\frac{1}{2}\) × (x – 3) × 12
= 6 (x – 3) वर्ग मी
प्रश्नानुसार,
आयताकार पार्क का क्षेत्रफल = त्रिभुजाकार पार्क का क्षेत्रफल + 4
x(x – 3) = 6(x – 3) + 4
x² – 3x = 6x – 18 + 4
x² – 3x – 6x + 14 = 0
x² – 9x + 14 = 0
x² – 7x – 2x + 14 = 0
x(x – 7) – 2(x – 7) = 0
(x – 7)(x – 2) = 0
यदि x – 7 = 0, तो x = 7
और यदि x – 2 = 0 तो x = 2 जो कि असम्भव है, क्योंकि अगर लम्बाई 2 मी. है तो चौड़ाई (x – 3) मी = – 1 मी होगी जो कि ऋणात्मक है।
अतः पार्क की लम्बाई = 7 मी
तथा चौड़ाई = (7 – 3) मी = 4 मी

प्रश्न 13.
कुछ लम्बाई वाले एक कपड़े की कुल लागत ₹ 200 है। यदि यह कपड़ा 5 मीटर अधिक लम्बा हो तथा प्रत्येक मीटर कपड़े की लागत ₹ 2 कम हो, तो कपड़े की कुल लागत में कोई परिवर्तन नहीं होगा। कपड़े का वास्तविक प्रति मीटर मूल्य ज्ञात कीजिए तथा कपड़े की लम्बाई भी ज्ञात कीजिए।
हल :
माना, कपड़े की लम्बाई x मी हैं तथा कपड़े के प्रत्येक मीटर का मूल्य y है।
प्रश्नानुसार,
xy = 200 ……..(i)
यदि कपड़े की लम्बाई 5 मी अधिक होतो तथा प्रत्येक मीटर का मूल्य ₹2 कम होता तो,
(x + 5)(y – 2) = 200
xy – 2x + 5y – 10 = 200 ……..(ii)
समीकरण (i) व (ii) को बराबर करने पर,
xy = xy – 2x + 5y – 10
2x – 5y = 10 ……..(iii)
2x – 5 × \(\frac{200}{x}\) = – 10 (समीकरण (i) से y = \(\frac{200}{x}\))
2x – \(\frac{1000}{x}\) = – 10
2x² – 1000 = – 10x
2x² + 10x – 1000 = 0
x² + 5x – 500 = 0
x² + 25x – 20x – 500 = 0
x(x + 25) – 20(x + 25) = 0
(x – 20)(x + 25) = 0
यदि x – 20 = 0, तो x = 20
और x + 25 = 0 तो x = – 25; जो कि असम्भव है, क्योंकि लम्बाई ऋणात्मक नहीं होती।
अब x × y = 200
20 × y = 200
y = 10
अतः कपड़े की लम्बाई 20 मीटर है तथा प्रत्येक मीटर का मूल्य ₹ 10 है।

प्रश्न 14.
दो पानी के नल एक साथ एक टैंक को 1\(\frac{7}{8}\) घंटों में भर सकते हैं। बड़े व्यास वाला नल टैंक को भरने में, कम व्यास वाले नल से 2 घंटे कम समय लेता है। प्रत्येक नल द्वारा अलग से टैंक को भरने का समय ज्ञात कीजिए।
हल :
माना छोटा नल टैंक को भरने में x घंटे लेता है।
∴ बड़ा नल टैंक को भरने में (x – 2) घंटे लेगा।
अब, 1 घंटे में बड़े नल द्वारा भरा गया पानी = \(\frac{1}{x-2}\)
1 घंटे में छोटे नल द्वारा भरा गया पानी = \(\frac{1}{x}\)
तथा 1 घंटे में दोनों नल द्वारा भरा गया पानी = \(\frac{8}{15}\)
\(\frac{1}{x}+\frac{1}{x-2}\) = \(\frac{8}{15}\)
\(\frac{x-2+x}{x(x-2)}\) = \(\frac{8}{15}\)
\(\frac{2 x-2}{x(x-2)}\) = \(\frac{8}{15}\)
\(\frac{x-1}{x(x-2)}\) = \(\frac{4}{15}\)
15x – 15 = 4x² – 8x
4x² – 8x – 15x + 15 = 0
4x² – 23x + 15 = 0
4x² – 20x – 3x + 15 = 0
4x(x – 5) – 3(x – 5) = 0
(x – 5) (4x – 3) = 0
यदि x – 5 = 0, तो x = 5
और यदि 4x – 3 = 0, तो x = \(\frac{3}{4}\) जो कि अमान्य है।
अतः छोटा नल को टैंक भरने में 5 घण्टे लगेंगे एवं बड़े नल को 3 घण्टे लगेंगे।

प्रश्न 15.
निम्न समीकरणों के मूल ज्ञात कीजिए :
(i) 8x² – 2x – 3 = 0
(ii) 14x² + 17x – 6 = 0
(iii) 3x² – 4\(\sqrt{3}\)x + 4 = 0
(iv) x² + 5x – (a² + a – 6) = 0
हल :
(i) दिया है,
8x² – 2x – 3 = 0
⇒ 8x² – 6x + 4x – 3 = 0
⇒ 2x(4x – 3) + 1(4x – 3) = 0
⇒ (4x – 3)(2x + 1) = 0
यदि 4x – 3 = 0, तो x = \(\frac{3}{4}\)
और यदि 2x + 1 = 0, तो x = –\(\frac{1}{2}\)
अत: x = \(\frac{3}{4}\), –\(\frac{1}{2}\)

(ii) दिया है, 14x² + 17x – 6 = 0
⇒ 14x² + 21x – 4x – 6 = 0
⇒ 7x(2x + 3) – 2(2x + 3) = 0
⇒ (2x + 3)(7x – 2) = 0
यदि 2x + 3 = 0, x = – \(\frac{3}{2}\)
और यदि 7x – 2 = 0, तो x = \(\frac{2}{7}\)
अत: x = –\(\frac{3}{2}\), \(\frac{2}{7}\)

(iii) दिया है,
3x² – 4\(\sqrt{3}\)x + 4 = 0
3x² – 2\(\sqrt{3}\)x – 2\(\sqrt{3}\)x + 4 = 0
\(\sqrt{3}\)x(\(\sqrt{3}\) – 2) – 2(\(\sqrt{3}\) – 2) = 0
(\(\sqrt{3}\) – 2) (\(\sqrt{3}\) – 2) = 0
यदि \(\sqrt{3}\)x – 2 = 0 तो x = \(\frac{2}{\sqrt{3}}\)
अतः x = \(\frac{2}{\sqrt{3}}\), \(\frac{2}{\sqrt{3}}\)

(iv) दिया है,
x² + 5x – (a² + a – 6) = 0
यहाँ, a² + a – 6 = a² + 3a – 2a – 6
= a(a + 3) – 2(a + 3)
= (a + 3)(a – 2)
∴ x² + 5x – (a – 3)(a – 2) = 0
x² + (a + 3)x – (a – 2)x – (a + 3)(a – 2) = 0
x[x + a + 3] – (a – 2)[x + a + 3] = 0
(x – a + 2)(x + a + 3) = 0
यदि x – a + 2 = 0, x = a – 2
और यदि x + a + 3 = 0, तो x = – (a + 3)
अत: x = (a – 2) और – (a + 3)

प्रश्न 16.
x के लिए हल कीजिए:

हल :

⇒ (4x + 1)(5x + 1) = 3(x² + 5x + 4)
⇒ 20x² + 4x + 5x + 1 = 3x² + 15x + 12
⇒ 17x² – 6x – 11 = 0
⇒ 17x² – 17x + 11x – 11 = 0
⇒ 17x(x – 1) + 11(x – 1) = 0
⇒ (x – 1)(17x + 11) = 0
⇒ x = 1 या x = \(\frac{-11}{17}\)
दिया है x ≠ 1, अतः x = \(\frac{-11}{17}\)

(ii) दिया है, \(\frac{1}{2 x-3}+\frac{1}{x-5}\) = 1\(\frac{1}{9}\)
\(\frac{x-5+2 x-3}{(2 x-3)(x-5)}\) = \(\frac{10}{9}\)
\(\frac{3 x-8}{2 x^2-13+15}\) = \(\frac{10}{9}\)
9(3x – 8) = 10 (2x² – 13x + 15)
27x – 72 = 20x² – 130x + 150
20x² – 157x + 222 = 0
20x² – 120x – 37x + 222 = 0
20x(x – 6) – 37 (x – 6) = 0
(x – 6) (20x – 37) = 0
(x – 6 ) = 0 या 20x – 37 = 0
अत: x = 6 या x = \(\frac{37}{20}\)

(iii)

5x² + 2x + 2 = 2(2x² – x – 1)
5x² + 2x + 2 = 4x² – 2x – 2
x² + 4x + 4 = 0
(x + 2)² = 0
या तो x + 2 = 0 या x + 2 = 0
अतः x = – 2, -2

प्रश्न 17.
दो नल एक साथ टैंक को 3\(\frac{1}{13}\) घण्टे में भर सकते हैं। यदि एक नल टैंक को भरने में दूसरे नल से 3 घण्टे अधिक लेता है, तो प्रत्येक नल टैंक को भरने में कितना समय लेगा ?
हल :
माना कि टैंक एक नल से x घण्टे में भरता है। अत: टैंक दूसरे नल से (x + 3) घण्टे में भरेगा।
टैंक को दोनों नल एक साथ भरते हैं = 3\(\frac{1}{13}\)
= \(\frac{40}{13}\) घण्टे में
प्रश्नानुसार,

13x² + 39x = 80x + 120
13x² – 41x – 120 = 0
13x² – 65x + 24x – 120 = 0
13x(x – 5) + 24 (x – 5) = 0
(x – 5)(13x + 24) = 0
यदि x – 5 = 0 तो x = 5
और यदि 13x + 24 = 0 तो x = – \(\frac{24}{13}\), जो कि संभव नहीं है।
अतः एक नल टैंक भरेगा = 5 घण्टे में।
और दूसरा नल टैंक भरेगा = (x – 3) = 8 घण्टे में ।

प्रश्न 18.
एक रेलगाड़ी 300 किमी की दूरी एकसमान चाल से तय करती है। यदि रेलगाड़ी की चाल 5 किमी / घंटा बढ़ा दी जाए, तो यात्रा में 2 घंटे कम समय लगता है। रेलगाड़ी की मूल चाल ज्ञात कीजिए।
हल :
माना, रेलगाड़ी की मूल चाल = x किमी / घंटा
रेलगाड़ी की नई चाल = (x + 5) किमी / घंटा
दूरी = 300 किमी
प्रश्नानुसार,
\(\frac{300}{x}-\frac{300}{x+5}\) = 2
⇒ \(\frac{300(x+5-x)}{(x)(x+5)}\) = 2
⇒ 1500 = 2(x² + 5x)
⇒ 1500 = 2x² + 10x
⇒ 2x² + 10x – 1500 = 0
⇒ x² + 5x – 750 = 0
⇒ x² + 30x – 25x – 750 = 0
⇒ x(x + 30) – 25 (x + 30) = 0
⇒ (x + 30)(x – 25) = 0
यदि x + 30 = 0 तो x = – 30, जो अमान्य है।
और यदि x – 25 = 0 तो x = 25
अतः रेलगाड़ी की मूल चाल = 25 किमी / घण्टा ।

प्रश्न 19.
A एक कार्य को करने में B से 6 दिन कम लेता है। यदि A और B दोनों एक साथ काम करते हुए इसे 4 दिन में कर सकते हैं, तो B इस कार्य को समाप्त करने में कितने दिन लेगा?
हल :
माना B कार्य को x दिन में समाप्त कर सकता है। तो A कार्य को (x – 6) दिन में समाप्त करेगा।
दोनों मिलकर कार्य 4 दिन में समाप्त करते हैं।
प्रश्नानुसार, \(\frac{1}{x}+\frac{1}{x-6}\) = \(\frac{1}{4}\)
⇒ \(\frac{x-6+x}{(x)(x-6)}\) = \(\frac{1}{4}\)
⇒ 4(2x – 6) = x² – 6x
⇒ 8x – 24 = x² – 6x
⇒ x² – 14x + 24 = 0
⇒ x² – 12x – 2x + 24 = 0
⇒ x (x – 12) – 2 (x – 12) = 0
⇒ (x – 12) (x – 2) = 0
यदि x – 12 = 0 तो x = 12
और यदि x – 2 = 0 तो x = 2 (अमान्य हैं।)
अतः B कार्य को करने में 12 दिन लेगा।
A कार्य को करने में 6 दिन लेगा।

प्रश्न 20.
एक नाव की शांत जब में चाल 15 किमी / घंटा है। यह नाव 30 किमी धारा के विपरीत दिशा में जाकर पुन: उसी जगह 4 घंटे 30 मिनट में वापस लौट आती है। धारा की चाल ज्ञात कीजिए।
हल :
माना धारा की चाल x किमी / घंटा है।
प्रश्नानुसार,

अतः धारा की चाल 5 किमी / घण्टा ।

प्रश्न 21.
एक आयताकार खेल का विकर्ण उसकी छोटी भुजा से मी अधिक लम्बा है। यदि बड़ी भुजा छोटी भुजा से 20 मी. अधिक हो, तो खेत की भुजाएँ ज्ञात कीजिए।
हल :
माना खेत की छोटी भुजा = x मी
∴ खेत की बड़ी भुजा = (x + 20) मी
और खेत का विकर्ण = (x + 40) मी
पाइथागोरस प्रमेय से,
(विकर्ण)² = शेष दोनों भुजाओं के वर्गों का योग
⇒ (x + 40)² = x² + (x + 20)²
⇒ x² + 1600 + 80x = x² + x² + 400 + 40x
⇒ x² – 2x² + 80x – 40 + 1600 – 400 = 0
⇒ – x² – 40x + 1200 = 0
⇒ x² + 40x – 1200 = 0
⇒ x² + 60x – 20x – 1200 = 0
⇒ x(x + 60) – 20(x + 60) = 0
⇒ (x + 60) (x – 20) = 0
यदि x + 60 = 0, तो x = – 60 जो कि असम्भव है, क्योंकि भुजा की लम्बाई ऋणात्मक नहीं हो सकती।
और यदि x – 20 = 0 तो x = 20
अतः खेत की छोटी भुजा = 20 मी
तथा खेत की बड़ी भुजा = (20 + 20) मी = 40 मी.

प्रश्न 22.
एक आयताकार खेत का विकर्ण उसकी छोटी भुजा से 25 मी अधिक लंबा है। यदि बड़ी भुजा छोटी भुजा से 23 मी अधिक है, तो खेत की भुजाएँ ज्ञात कीजिए ।
हल :
माना रेलगाड़ी की चाल x किमी / घंटा है।
300 किमी दूरी तय करने में लगा समय = \(\frac{300}{x}\) घंटे
रेलगाड़ी की नई चाल = (x + 10) किमी / घंटा
नई चाल से 300 किमी दूरी तय करने में लगा समय = \(\frac{300}{x+10}\) घंटे
प्रश्नानुसार,
\(\frac{300}{x}-\frac{300}{x+10}\) = 1
⇒ \(\frac{300[x+10-x]}{x(x+10)}\) = 1
⇒ 300 × 10 = x(x + 10)
⇒ x² + 10x – 3000 = 0
⇒ x² + 60x – 50x – 3000 = 0
⇒ x(x + 60) – 50 (x + 60) = 0
⇒ (x + 60) (x – 50) = 0
यदि x + 60 = 0, तो x = – 60; असम्भव क्योंकि चाल ऋणात्मक नहीं होती।
और यदि x – 50 = 0 तो x = 50
अतः रेलगाड़ी की चाल = 50 किमी / घंटा

रिक्त स्थानों की पूर्ति कीजिए :

प्रश्न (क)

1. ऐसा व्यंजक जिसमें चर की घात ……………….. होती है, द्विघात बहुपद कहलाता है।
2. समीकरण x² + bx + c = 0 के मूल बराबर हैं, यदि ………………. है।
3. द्विघात समीकरण 3x² – 2x + 4 = 0 के मूल ……………….. होंगे।
4. समीकरण 9x² = 10 का मानक रूप ………………….. है।
5. प्रत्येक द्विघात समीकरण के अधिक से अधिक ………………. वास्तविक मूल हो सकते हैं।

हल :

1. 2
2. b² – 4c = 0
3. काल्पनिक
4. 9x² + 0x – 10 = 0
5. दो

निम्न में से सत्य / असत्य कथन छाँटिए :

प्रश्न (ख)

1. द्विघात समीकरण ax² + bx + c = 0 का विविक्तर, D = b² + 4ac होता है।
2. यदि b² – 4ac > 0 तथा पूर्ण वर्ग हो, तो मूल वास्तविक, परिमेय तथा असमान होते हैं।
3. यदि b² – 4ac > 0 तथा पूर्ण वर्ग न हो, तो मूल वास्तविक, अपरिमेय तथा असमान होते हैं।
4. यदि b² – 4ac < 0 तो मूल काल्पनिक होते हैं।
5. यदि b² – 4ac = 0 तो मूल काल्पनिक, परिमेय तथा असमान होते हैं।

हल :

1. असत्य,
2. सत्य,
3. सत्य,
4. सत्य,
5. असत्य

(ग) बहुविकल्पीय प्रश्न :

प्रश्न 1.
बहुपद x² – 3x – m (m + 3) के शून्यक हैं:
(A) m, m + 3
(B) – m, m + 3
(C) m, – (m + 3)
(D) – m, – (m + 3)
हल :
शून्यक के लिए : x² – 3x – m(m + 3) = 0
x² – (3 + m – m)x – m(m + 3) = 0
x² – (m + 3)x + mx – m(m + 3) = 0
x[x – (m + 3)] + m[x – (m + 3)] = 0
[x – (m + 3)] (x + m) = 0
यदि [x – (m + 3)] = 0, तो x = m + 3
यदि x + m = 0, तो x = – m
अत: विकल्प (B) सही है।

प्रश्न 2.
द्विघात समीमरण x² – 0.04 = 0 के मूल हैं:
(A) ± 0.2
(B) ± 0.02
(C) 0.4
(D) 2
हल :
दिया है, x² – 0.04 = 0
x² = 0.04 = \(\frac{4}{100}\)
x = ± \(\sqrt{\frac{4}{100}}\)
= ± \(\frac{2}{10}\) = ± 0.2
अत: सही विकल्प (A) है।

प्रश्न 3.
λ का वह मान जिसके लिए (x² + 4x + λ) एक पूर्ण वर्ग है, है:
(A) 16
(B) 9
(C) 1
(D) 4
हल :
दिया है, x² + 4x + λ
= (x)² + 2(2) x + λ
= (x)² + 2(2) x + (2)²
= (x + 2)², जो कि एक पूर्ण वर्ग है।
∴ λ = (2)² = 4
अत: सही विकल्प (D) है।

प्रश्न 4.
द्विघात समीकरण x² – 4x + k = 0 के दो भिन्न वास्तविक मूल होंगे, यदि
(A) k = 4
(B) k > 4
(C) k = 16
(D) k < 4
हल :
दो भिन्न वास्तविक मूलों के लिए प्रतिबन्ध :
B² – 4AC > 0
⇒ (-4)² – 4 × 1 × k > 0
⇒ 16 – 4k > 0
⇒ – 4k > – 16
⇒ k < 4
अत: सही विकल्प (D) है।

प्रश्न 5.
यदि द्विघात समीकरण 2x² + kx + 2 = 0 के मूल समान हों, तो का मान है :
(A) 4
(B) ± 4
(C) – 4
(D) = 0
हल :
मूलों के समान होने के लिए प्रतिबन्ध :
B² – 4AC = 0
⇒ (k)² – 4 × 2 × 2 = 0
⇒ k² – 16 = 0
⇒ k² = 16
⇒ k = ± 4
अत: सही विकल्प (B) है।

प्रश्न 6.
द्विघात समीकरण 2x² – 4x + 3 = 0 के मूल हैं:
(A) वास्तविक तथा बराबर
(B) वास्तविक तथा भिन्न
(C) वास्तविक नहीं
(D) वास्तविक
हल :
यहाँ B² – 4AC = (-4)² – 4 × 2 × 3
= 16 – 24 = – 8
⇒ B² – 4AC < 0
अत: सही विकल्प (C) है।

प्रश्न 7.
समीकरण ax² + bx + c = 0, a ≠ 0 के मूल वास्तविक नहीं होंगे यदि :
(A) b² < 4ac
(B) b² > 4ac
(C) b² = 4ac
(D) b = 4ac
हल :
सही विकल्प (A) है।

प्रश्न 8.
द्विघात समीकरण px² + qx + r =0, p ≠ 0 के मूल समान होंगे यदि :
(A) p² < Apr
(B) p² > 4qr
(C) p² = 4pr
(D) p² = 4qr
हल :
सही विकल्प (C) है।

प्रश्न 9.
द्विघात समीकरण 2x² – x – 6 = 0 के मूल है :
(A) – 2, \(\frac{3}{2}\)
(B) 2, – \(\frac{3}{2}\)
(C) – 2, – \(\frac{3}{2}\)
(D) 2, \(\frac{3}{2}\)
हल :
दिया गया द्विघात समीकरण है :
2x² – x – 6 = 0
⇒ 2x² – (4 – 3) x – 6 = 0
⇒ 2x² – 4x + 3x – 6 = 0
⇒ (2x² – 4x) + (3x – 6) = 0
⇒ 2x(x – 2) + 3(x – 2) = 0
⇒ (x – 2) (2x + 3) = 0
⇒ x = – 2 = 0 या 2x + 3 = 0
⇒ x = 2 या x = \(\frac{-3}{2}\)
अत: विकल्प (B) सही है।

प्रश्न 10.
द्विघात समीकरण 2x² – \(\sqrt{5}\)x + 1 = 0 के :
(A) दो भिन्न वास्तविक मूल है
(B) दो बराबर वास्तविक मूल है
(C) कोई वास्तविक मूल नहीं है
(D) दो से अधिक वास्तविक मूल है।
हल :
सही विकल्प (C) है।

प्रश्न 11.
यदि f(x) = ax² + bx + c और c = \(\frac{b^2}{4 a}\) हो, तो f(x) = 0 के मूल होंगे :
(A) वास्तविक और बराबर
(B) वास्तविक और असमान
(C) वास्तविक नहीं
(D) इनमें से कोई नहीं
हल :
सही विकल्प (A) है।

प्रश्न 12.
यदि p(x) एक बहुपद में चर x इस प्रकार है कि p(h) = 0 हो तो h, p(x) का
(A) मूल है
(B) गुणनखण्ड है
(C) शून्यक है
(D) इनमें से कोई नहीं ।
हल :
सही विकल्प (C) है।

प्रश्न 13.
बहुपद p(x) में x इस तरह कि p (h) = 0 हो, तो p(x), p(x – h) :
(A) मूलं है.
(B) गुणनखण्ड है
(C) शून्यक है
(D) इनमें से कोई नहीं
हल:
सही विकल्प (B) है।

प्रश्न 14.
दो संख्याएँ ज्ञात कीजिए जिनका योग 27 और गुणनफल 182 हो :
(A) 13 और 14
(C) 17 और 10
(B) 15 और 12
(D) इनमें से कोई नहीं
हल :
सही विकल्प (A) है।

प्रश्न 15.
यदि द्विघात समीकरण x² (a² + b) + 2x( ac + bad) + (c2 + 2) = 0 के मूल बराबर हों तो :
(A) ad = – bc
(B) ad = ± bc
(C) ad = bc
(D) इनमें से कोई नहीं
हल :
सही विकल्प (A) है।

Jharkhand Board JAC Class 10 Science Solutions Chapter 1 Chemical Reactions and Equations Textbook Exercise Questions and Answers.

JAC Board Class 10 Science Solutions Chapter 1 Chemical Reactions and Equations

Jharkhand Board Class 10 Science Chemical Reactions and Equations Textbook Questions and Answers

Question 1.
Which of the statements about the reaction below are incorrect?
2PbO(s) + C(s) → 2Pb(s) + CO₂(g)
(a) Lead is getting reduced.
(b) Carbon dioxide is getting oxidised.
(c) Carbon is getting oxidised.
(d) Lead oxide is getting reduced.
(i) (a) and (b)
(ii) (a) and (c)
(iii) (a), (b) and (c) (iv) all
Answer:
(i) (a) and (b) s

Question 2.
Fe₂O₃ + 2Al → Al₂O₃ + 2Fe
The above reaction is an example of a…
(a) combination reaction.
(b) double displacement reaction.
(c) decomposition reaction.
(d) displacement reaction.
Answer:
(d) displacement reaction.

Question 3.
What happens when dilute hydrochloric acid is added to iron fillings?
(a) Hydrogen gas and iron chloride are s produced.
(b) Chlorine gas and iron hydroxide are produced.
(c) No reaction takes place.
(d) Iron salt and water are produced,
Answer:
Hydrogen gas and iron chloride are produced.

Question 4.
What is a balanced chemical equation? Why should chemical equations be balanced?
Answer:
A chemical reaction in which atoms of $ different elements of reactant and product side are equal then the chemical equation S is called balanced chemical equation.

Now, according to the law of conservation of mass, matter can neither be created, nor be destroyed. Hence in a chemical reaction, mass of reactants S should be equal to the mass of products.

Number of atoms of each element should be equal on both side of the reaction for keeping mass constant.
Hence, it is essential to balance the chemical equation.

Question 5.
Translate the following statements into chemical equations and then balance them:
(a) Hydrogen gas combine with nitrogen to form ammonia.
(b) Hydrogen sulphide gas burns in air to give water and sulphur dioxide.
(c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.
(d) Potassiam metal reacts with water to give potassium hydroxide and hydrogen gas.
Answer:

Question 6.
Balance the following chemical equations:
(a) HNO₃ + Ca(OH)₂ → Ca(NO₃)₂ + H₂O
(b) NaOH + H₂SO₄ → Na₂SO₄ + H₂O
(c) NaCl + AgNO₃ → AgCl + NaNO₃
(d) BaCl₂ + H₂SO₄ → BaSO₄ + HCl
Answer:
(a) 2HNO₃ + Ca(OH)₂ → Ca(NO₃)₂ + 2H₂O
(b) 2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O
(c) NaCl + AgNO₃ → AgCl + NaNO₃
(d) BaCl₂ + H₂SO₄ → BaSO₄ + 2HCl

Question 7.
Write the balanced chemical equations for the following reactions :
(a) Calcium hydroxide + Carbon dioxide → Calcium carbonate + Water
(b) Zinc + Silver nitrate → Zinc nitrate + Silver
(c) Aluminium + Copper chloride → Aluminium chloride + Copper
(d) Barium chloride + Potassium sulphate → Barium sulphate + Potassium chloride
Answer:

Question 8.
Write the balanced chemical equation for the following and identify the type of reaction in each case :
(a) Potassium bromide (aq) + Barium iodide(aq) → Potassium iodide(aq) + Barium bromide (s)
(b) Zinc carbonate(s) → Zinc oxide (s) + Carbon dioxide (g)
(c) Hydrogen (g) + Chlorine (g) → Hydrogen chloride (g)
(d) Magnesium (s) + Hydrochloric acid(aq) → Magnesium chloride(aq) + Hydrogen(g)
Answer:
(a) 2KBr(aq) + Bal₂(aq) → 2KI(aq) + BaBr₂(s)
The given reaction is a double displacement reaction.

Given reaction is a thermal decomposition reaction.

(c) H₂(g) + Cl₂(g) → 2HCl(g)
Given reaction is a combination reaction.

(d) Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g)
Given reaction is a displacement reaction.

Question 9.
What does one mean by exothermic and endothermic reactions? Give examples.
Answer:
Exothermic reaction : A chemical reaction in which heat energy is evolved during the formation of product is called an exothermic reaction.

For example, Combustion of natural gas (methane) is an exothermic reaction.
CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(g) + heat

Endothermic reaction : A chemical reaction in which heat is absorbed during the formation of products is called an endothermic reaction.
For example, Decomposition of silver chloride in presence of sunlight is called an endothermic reaction.

Question 10.
Why is respiration considered an exothermic reaction? Explain.
Answer:
We need energy for staying alive. We get S this energy from the diet (food), we eat. Food is broken down into simple substances during digestion.

For example, Rice, potatoes and bread consists of carbohydrates. These carbohydrates are broken down to form glucose. This glucose combines with oxygen in the cells of our body and provides energy. This reaction (process) is called respiration. Thus, energy is released during respiration process, it is called an exothermic reaction.
C₆H₁₂O₆(aq) + 6O₂(aq) → 6CO₂(aq) + 6H₂O(1) + Energy

Question 11.
Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.
Answer:
In decomposition reaction, a single molecule of reactant by absorbing heat is broken down into two or more products (atoms), while in combination reaction, opposite phenomenon to decomposition reaction is observed. In combination reaction, two or more substances (elements or compounds) combine to form a single product with heat change.

Decomposition reactions :
AB + Energy → A + B

Combination reactions :
A + B > AB + Energy
C(s) + O₂(g) → CO₂(g) + Energy

Question 12.
Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity.
Answer:

Question 13.
What is the difference between displacement and double displacement reactions? Write equations for these reactions.
Answer:
In displacement reaction, more reactive element displaces less reactive element from its solution. For example, In case of Zn and Ag, Zn being more reactive than Ag, it displaces Ag from its solution of AgNO₃.
(i) Zn(s) + 2AgNO₃(aq) → Zn(NO₃)₂(aq) + 2Ag(s)
Similarly, Fe being more reactive displaces Cu from CuSO₄ solution.

(ii) Fe(s) + CuSO₄(aq) → FeSO₄(aq) + Cu(s)
In double displacement reaction, two / compounds exchange their ions to form s two new compounds.
For example,

• Na₂SO₄(aq) + BaCl₂(aq) → BaSO₄(s) + 2NaCl(aq)
• 2KBr(aq) + BaI₂(aq) → 2KI(aq) + BaBr₂(s)

Question 14.
In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved.
Answer:
Cu(s) + 2AgNO₃(aq) → Cu(NO₃)₂(aq) + 2Ag(s)

Question 15.
What do you mean by a precipitation reaction? Explain by giving examples.
Answer:
Chemical reaction, in which reactants react to form insoluble precipitate is called precipitation reaction.
For example,

Question 16.
Explain the following in terms of gain or loss of oxygen with two examples each:
(a) Oxidation (b) Reduction
Answer:
(a) Oxidation: It is a reaction in which atom or molecule gains oxygen or loses hydrogen.
For example,
C + O₂ → CO₂
2Cu + O₂ → 2CuO
In above reactions, ‘C’ and ‘Cu’ undergo Oxidation.

(b) Reduction : It is a reaction in which atom or molecule loses oxygen or gains hydrogen.
For example,
CuO + H₂ → Cu + H₂0
CO₂ + H₂ → CO + H₂O
In above reactions, ‘CuO’ and ‘CO₂’ undergo reduction.

Question 17.
A shiny brown coloured element ‘X’ on heating in air becomes black in colour. Name the element ‘X’ and the black coloured compound formed.
Answer:
Here, element ‘X’ is copper (Cu). When it is heated in air, it forms black coloured copper oxide (CuO).
For example,

In this reaction, Cu is oxidised to CuO.

Question 18.
Why do we apply paint on iron articles?
Answer:
Iron objects undergo rusting due to metal corrosion; hence, surface of iron is coated with paint to prevent it from rusting. As a result, iron does not come in contact with air. Thus, iron objects remain safe for longer period and rusting does not occur.

Question 19.
Oil and fat containing food items are flushed with nitrogen. Why?
Answer:
Food items containing oil and fat reacts with oxygen and become rancid. Such food items have bad smell and are harmful to health. Hence, to prevent the spoilage of food items, they are flushed with unreactive gas like nitrogen, which acts as an antioxidant.

Question 20.
Explain the following terms with one example each:
(a) Corrosion
(b) Rancidity
Answer:
(a) Corrosion:
Metal gets corroded in the presence of acid and moisture. This process is called corrosion. Rusting of iron, tarnishing of silver, green coating of salt on the utensils of copper are the examples of corrosion.

• Due to corrosion, iron gets covered with a red brown substance (powder) which is called rusting of iron (or corrosion).
• Corrosion causes damage to the articles (objects) made from iron such as car-bodies, bridges, iron railings, ships, etc. There is a huge expenditure to control corrosion.
• Rusting can be prevented by painting the surface of iron or coating the surface of iron with more reactive metal (Zn).
• Prevention of corrosion by coating iron surface with zinc is called galvanisation.

(b) Rancidity:
When food containing oil and fat is kept in an open air, it undergo oxidation and become rancid; due to which their smell and taste changes. This process is called rancidity.

Usually, to avoid rancidity in food containing oil and fat, substances are added which prevent oxidation. Such substances are known as antioxidant substances. Food kept in air-tight containers helps to slow down its oxidation and rancidity is retarded.

Manufacturers of potato chips flush bags of chips with gas such as inactive nitrogen gas as antioxidant to prevent the oxidation of potato chips.

Jharkhand Board Class 10 Science Chemical Reactions and Equations InText Questions and Answers

Question 1.
Why should a magnesium ribbon be cleaned before burning in air?
Answer:
Magnesium ribbon is more reactive and when it is exposed to air, a layer of MgO is formed on its surface.
2Mg(s) + O₂(g) → 2MgO(s)
This layer of MgO is removed by rubbing with sand paper before burning in air. Therefore, magnesium ribbon easily reacts with oxygen. Thus, magnesium ribbon is cleaned before burning in air.

Question 2.
Write the balanced equation for the following chemical reactions :
(1) Hydrogen + Chlorine → Hydrogen chloride
(2) Barium chloride + Aluminium sulphate Barium sulphate + Aluminium chloride
(3) Sodium + Water → Sodium hydroxide + Hydrogen
Answer:
(1) H₂(g) + Cl₂(g) 2HCl(g)
(2) 3BaCl₂(aq) + Al₂(SO₄)₃(aq) → 3BaSO₄(s) + 2AlCl₃(aq)
(3) 2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)

Question 3.
Write a balanced chemical equation with physical state symbols for the following reactions :
(1) Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and the solution of sodium chloride.
(2) Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water.
Answer:

Question 4.
A solution of a substance ‘X’ is used for whitewashing.
(1) Name the substance ‘X’ and write its s formula.
(2) Write the reaction of the substance ‘X’ named in (1) above with water.
Answer:
(1) Substance X is calcium oxide. Its formula is CaO.

(2) Calcium oxide reacts vigorously with water and forms slaked lime (Ca(OH)₂) and liberates large amount of heat. It is an exothermic reaction.
CaO(s) + H₂O(l) → Ca(OH)₂(aq) + Heat

Question 5.
Why is the amount of gas collected s in one of the test tubes in activity 1.7 double of the amount collected in the other? Name these gases.
Answer:
Hydrogen and oxygen are obtained separately during the electrolysis of water. Water is made-up of two parts of hydrogen and one part of oxygen. Hence, two parts of hydrogen gas in one test tube and one part of oxygen l gas in another test tube are obtained during the electrolysis of water. Hence, hydrogen and oxygen gases are obtained in the ratio of 2 : 1 by volume.

Question 6.
Why does the colour of copper sulphate solution change, when an iron nail ( is dipped in it?
Answer:
When an iron nail is dipped in copper s sulphate solution, iron being more reactive than l copper, it displaces copper from the solution, s As a result, iron sulphate is formed, which is green in colour. Thus, colour of copper sulphate s solution changes.

Question 7.
Give an example of double displacement reaction other than the one ? given in activity 1.10.
Answer:
When sodium carbonate reacts with calcium chloride, it forms a precipitate of calcium S carbonate and sodium chloride. In this reaction, ( exchange of carbonate and chloride ions form two 5 new compounds.

This is double displacement reaction.

Question 8.
Identify the substances that are oxidised and the substances that are reduced in the following reactions:
(1) 4Na(s) + O₂(g) → 2Na₂O(s)
(2) CuO(s) + H₂(g) → Cu(s) + H₂O(1)
Answer:
(1) 4Na(s) + O₂(g) → 2Na₂O(s)
In this reaction, sodium (Na) metal is oxidised to Na₂0 and O₂ is reduced.

(2) CuO(s) + H₂(g) → Cu(s) + H₂O(1)
In this reaction, CuO is reduced to Cu, while H₂ is oxidised to H₂O.

Activity 1.1 [T. B. Pg. 1]

Aim : To study the burning of magnesium ribbon in air.

Caution: It is necessary that this activity should be performed in the presence of a teacher. For safety purpose, teacher and student should wear goggles.

Activity:

• Take approximately 3-4 cm long magnesium ribbon and make it clean by rubbing it with sand paper.
• Hold it with a pair of tongs and heat on the flame of burner or spirit lamp and the ash being formed collects in the watch-glass as shown in the figure 1.1.
• Collected ash in the watch-glass is of magnesium oxide.
• Burn the magnesium ribbon. Keeping it away as far as possible from your eyes.
  

Questions:

Question 1.
Why is magnesium ribbon selected?
Answer:
Magnesium ribbon is highly reactive and burns easily in air.

Question 2.
What is the colour of magnesium ribbon initially?
Answer:
Magnesium ribbon, initially, rubbed with sand paper appears silvery white.

Question 3.
Which type of flame is formed during the burning of magnesium ribbon?
Answer:
Magnesium ribbon burns with dazzling white flame in the flame of burner.

Question 4.
What is the composition of ash collected in watch-glass?
Answer:
White ash collected in watch-glass is of magnesium oxide (MgO).
Note: Due to O₂ and N₂ present in air, MgO is formed as a major product, moreover traces of Mg₃N₂ is also obtained.

Question 5.
Write the chemical reaction of forming the magnesium oxide.
Answer:

Activity 1.2 [T.B.Pg.2]

Aim : To study the reaction between lead nitrate and potassium iodide.

Activity:

• Take lead nitrate solution in a test tube.
• Add the solution of potassium iodide in it.

Questions :

Question 1.
What is the colour of lead nitrate solution?
Answer:
Lead nitrate solution is colourless.

Question 2.
What is the colour of an aqueous solution of potassium iodide?
Answer:
The solution of potassium iodide is colourless.

Question 3.
Write the balanced chemical equation for the reaction that takes place between lead nitrate and potassium iodide.
Answer:
Pb(NO₃)₂(aq) + 2KI(aq) → PbI₃(s) + 2KNO₃

Question 4.
What is the colour of PbI₂?
Answer:
PbI₂ is yellow.

Question 5.
Identify the type of the above reaction.
Answer:
This reaction is a double displacement reaction.

Activity 1.3 [T. B. Pg. 2]

Aim : To study the reaction between zinc metal and dilute sulphuric acid.

Caution: Use the acid with care.

Activity:

• Take a conical flask.
• Add a piece of zinc granules in it.
• Then add dilute hydrochloric acid or dilute sulphuric acid.
  

Questions :

Question 1.
What appears around the zinc granules?
Answer:
The granules of zinc react with dilute hydrochloric acid evolving hydrogen gas. Hence, bubbles of hydrogen gas appear around granules of zinc.

Question 2.
What happens to the conical flask?
Answer:
Conical flask becomes hot which can be felt on touching to it.

Question 3.
State the reaction occurring between the pieces of zinc and dilute HC1.
Answer:
Zn(s) + 2HCl(aq) → ZnCl₂(aq) + H₂(g)

Question 4.
Which type of reaction takes place between the pieces of zinc and dilute HCl?
Answer:
Reaction taking place between zinc granules and dilute HCl is an exothermic reaction.

Activity 1.4 [T. B. Pg. 6]

Aim: To study the reaction between calcium oxide and water.

Activity:

• Take some quick lime (Calcium oxide – CaO) in a beaker. Add water to it slowly.
• Touch the beaker as shown in the figure 1.3.
  

Questions:

Question 1.
What is formed by reaction of quick lime with water? Write reaction.
Answer:
The reaction between quick lime and water forms Ca(OH)₂.
CaO(s) + H₂O(l) → Ca(OH)₂(aq)

Question 2.
What is called the reaction occurring between quick lime and water?
Answer:
Reaction occurring between slaked lime and water is called slaking of lime.

Question 3.
What do you feel by touching the beaker outside?
Answer:
By touching the beaker, it is observed that the beaker becomes warm since, heat is evolved during reaction.

Question 4.
What is slaked lime?
Answer:
Calcium hydroxide (Ca(OH)₂) is known as slaked lime.

Activity 1.5 [T. B. Pg. 8]

Aim: To study the decomposition of ferrous sulphate on heating

Activity:

• Take approximately 2 g of ferrous sulphate crystals in a dry boiling tube.
• Heat the boiling tube over the flame of a burner.
• Observe the colour of the ferrous sulphate crystals carefully during the heating.
• Observe the colour of the crystals after heating it.
  

Questions :

Question 1.
What is the colour of crystals of ferrous sulphate?
Answer:
The crystals of ferrous sulphate are greenish (or faint or light green).

Question 2.
Which colour is observed on heating the crystals of ferrous sulphate?
Answer:
On heating the ferrous sulphate, it is decomposed into Fe2O₃ and green colour changes to (reddish) brown.

Question 3.
On heating ferrous sulphate in boiling tube, a gas evolved which has a characteristic smell. What is its reason?
Answer:
On heating ferrous sulphate, a gas having specific smell is evolved due to combustion of sulphur. The combustion of sulphur forms SO₂(g) and SO₃(g) which possesses strong irritating smell.

Activity 1.6 [T. B. Pg. 8]

Aim : To study the decomposition of lead nitrate.

Activity:

• Take about 2 g of lead nitrate powder in a boiling tube.
• Hold the boiling tube with a pair of tongs and heat it over the flame of a burner.
  

Questions :

Question 1.
Which gas is evolved from boiling tube on heating lead nitrate?
Answer:
Nitrogen dioxide (NO₂) is evolved from the boiling tube on heating lead nitrate. It is brown coloured gas.

Question 2.
Write the equation of reaction of heating lead nitrate.
Answer:

Activity 1.7 [T. B. Pg. 9]

Aim : To study electrolysis of water.

Activity:

• Take a plastic mug. Drill two holes at the base of the mug. Fix two rubber corks in it; as shown in the figure 1.6.
• Arrange the: test tubes in inverted position such that carbon electrodes remains in it as shown in the figure.
• Add water in a mug such that electrodes are immersed.
• Add a few drops of dilute sulphuric acid to water.
• Connect electrodes to a 6 volt battery.
• Now, switch on the current and leave the apparatus undisturbed for some time.
  

Questions :

Question 1.
What is an electrode?
Answer:
Platinum or carbon rod which remains dipped in the solution of electrolyte and on the surface of which chemical reactions occur is known as an electrode.

Question 2.
Which gas is evolved at anode during electrolysis of water?
Answer:
Oxygen gas is evolved at anode during electrolysis of water.

Question 3.
Which gas is evolved at cathode during electrolysis of water?
Answer:
Hydrogen gas is evolved at cathode during elecrolysis of water.

Question 4.
Are the volumes of the gases collected during electrolysis are same?
Answer:
No

Question 5.
State the chemical equation of reaction of electrolysis of water.
Answer:

Question 6.
What happens when O₂(g) and H₂[g) evolved are brought close to the burning candle?
Answer:
O₂(g) does not burn, while H₂(g) burns with popping sound.

Activity 1.8 [T. B. Pg. 9]

Aim : To study photochemical decomposition of silver chloride.

Activity:

• Take about 2 g of silver chloride in a china dish.
• Put this china dish in sunlight for some-time.
  

Questions :

Question 1.
What was the colour of silver chloride before exposure to sunlight?
Answer:
Silver chloride was white in colour before its exposure to sunlight.

Question 2.
What is the change in colour of silver chloride during its exposure to sunlight for sometime?
Answer:
When silver chloride is exposed to sunlight for sometime, its white colour changes to grey.

Question 3.
State tire chemical equation of decomposition reaction of silver chloride and silver bromide in presence of sunlight.
Answer:

Question 4.
Does the decomposition of silver bromide occur in sunlight?
Answer:
Yes

Question 5.
State the uses of AgCl and AgBr.
Answer:
AgCl and AgBr are used in black and white photography in films.

Activity 1.9 [T. B. Pg. 10]

Aim : To study the displacement reaction taking place between iron nail and solution of copper sulphate.

Activity:

• Take three iron nails and clean their surface by rubbing them with a sand paper.
• Take two test tubes labelled as (A) and (B). Take about 10 mL solution of copper sulphate in each test tube.
• Tie two iron nails with a thread and immerse them in copper sulphate solution for about 20 minutes.
  Keep one iron nail aside for comparison.
• Take out the iron nails from the copper sulphate solution after 20 minutes.
• Compare the colour of both iron nails with the nail kept aside.
• Compare the intensity of the colour of copper sulphate solutions of both the test tubes, (A) and (B).
  

Questions:

Question 1.
What would be the colour of iron nail placed in the solution of CuSO₄ ?
Answer:
Iron nail become brownish in colour.

Question 2.
What would be the change in colour of solution of copper sulphate ?
Answer:
Blue colour of copper sulphate solution fades (or becomes light blue).

Question 3.
Which reaction takes place when iron nail is dipped in the solution of copper sulphate ?
Answer:

Question 4.
What type of chemical reaction occur, when iron nail is dipped in copper sulphate solution?
Answer:
Reaction of iron nail with the solution of copper sulphate is a displacement reaction.

Activity 1.10 [T. B. Pg. 11]

Aim: To study double displacement reaction between barium chloride and sodium sulphate.

Activity:

• Take about 3 mb of sodium sulphate solution in a test tube.
• In another test tube, take about 3 mL of barium chloride solution.
• Mix the two solutions as shown in the figure.
  

Questions:

Question 1.
What is the colour of sodium sulphate and barium chloride solutions?
Answer:
Sodium sulphate and barium chloride are colourless solutions.

Question 2.
Which precipitate is obtained by mixing the solution of sodium sulphate and barium chloride ? Mention its colour.
Answer:
When solutions of sodium sulphate and barium chloride are mixed, a precipitate of barium sulphate (BaSO₄) is formed, which is white in colour.

Question 3.
Write a balanced chemical equation for the reaction between barium chloride and sodium sulphate.
Answer:
BaCl₂(aq) + Na₂SO₄(aq) → BaSO₄(s) + 2NaCl(aq)

Question 4.
What type of chemical reaction takes place between barium chloride and sodium sulphate?
Answer:
A chemical reaction taking place between barium chloride and sodium sulphate is a double displacement reaction.

Activity 1.11 [T. B. Pg. 12]

Aim: To study oxidation of copper to copper oxide.

Activity:

• Take 1 g of copper powder in a china dish and heat it as shown in the figure 1.10.
  

Questions:

Question 1.
What happens on heating the copper powder?
Answer:
Copper powder, on heating forms copper (II) oxide on its surface.

Question 2.
State the colour of copper oxide.
Answer:
The colour of copper oxide is black.

Question 3.
What type of reaction is represented by the reaction of formation of copper oxide from copper?
Answer:
The reaction of formation of copper oxide from copper is an oxidation reaction.

Question 4.
Which product is obtained by passing hydrogen gas over hot copper oxide?
Answer:
Copper is obtained by passing hydrogen gas over hot copper oxide.

Question 5.
Name the reaction of forming copper from copper oxide.
Answer:
The reaction to form copper from copper oxide is a reduction reaction.