NCERT Class 7 Science Chapter 3 - Fibre to Fabric Extra Questions

Chapter 3 - Fibre to Fabric Extra Questions

Fill in the Blanks
1.
Silk and wool fibres are obtained from animals.

2. Wool is obtained from the
fleece (hair) of sheep or yak.

3. Silk fibres come from
cocoons of the silk moth.

4. Hair trap a lot of air as air is a
poor conductor of heat.

5. Silkworms are
larvae of silk moth.

6. There are 2 types of sheep fibres. They are the
coarse beard hair, and the fine soft under-hair close to the skin.

7. The process of selecting parents for obtaining special characters in their offspring, such as soft under hair in sheep is called
selective breeding.

8. Mohair is obtained from
angora goats which are found in hilly regions.

9. Llama and Alpaca, found in
South America, also yield wool.

10. In
Rajasthan and Punjab, Lohi breed of sheep is found.

11. The
Marwari and Patanwadi breed of sheep are found in Gujarat.

12. The fleece of the sheep along with a thin layer of skin is removed from its body. This process is called
shearing.

13. The sheared skin with hair is thoroughly washed in tanks to remove grease, dust and dirt. This is called
scouring.

14. After scouring,
sorting is done.

15. The small fluffy fibres are called
burrs.

16. The rearing of silkworms for obtaining silk is called
sericulture.

17. The female silk moth lays eggs, from which hatch larvae which are called
caterpillars or silkworms.

18. The caterpillar secretes fibre made of a
protein which hardens on exposure to air and becomes silk fibre.

19. The most common silk moth is the
mulberry silk moth.

20. The process of taking out threads from the cocoon for use as silk is called
reeling the silk.

21. A
yarn is a long continuous thread.

22.
China is the largest producer of silk.

23. Silk is a
poor conductor of heat.

Answer the following questions:
24. Name the sources of obtaining fibres.
Answer:
The sources of obtaining fibres are plants and animals.

25. Name some wool yielding animals.
Answer:
Wool yielding animals include sheep, yak, llama, alpaca, angora goat, angora rabbit and camel etc.

26. What are the 2 types of fibres of sheep?
Answer:
The 2 types of fibres of sheep are
• the coarse beard hair
• the fine soft under-hair close to the skin

27. How do the hair of certain animals help in keeping their bodies warm?
Answer:
Hair traps a lot of air which is a poor conductor of heat. And therefore the hair keeps their body warm.

28. Name the goats which are found in Tibet and Ladakh.
Answer:
The goats found in Tibet and Ladakh region are the angora goats.

29. Where are wool yielding animals Llama and Alpaca found?
Answer:
Llama and alpaca are found in South America.

30. Define shearing.
Answer:
The fleece of the sheep along with a thin layer of skin is removed from its body. This process is called shearing.

31. What is the second step for processing fibres into wool? Give an account of it.
Answer:
The second step for processing fibres into wool is Scouring. The process in which the sheared skin with hair is thoroughly washed in tanks to remove grease, dust and dirt. Nowadays scouring is done by machines.

32. Which two fibres are made up of proteins?
Answer:
Silk and wool are two fibres which are made up of proteins.

33. Explain in brief about the processes that are required for processing fibres into wool.
Answer:

• Step I: The fleece of the sheep along with a thin layer of skin is removed from its body. This process is called shearing. Usually, hair are removed during the hot weather. This enables sheep to survive without their protective coat of hair. The hair provide woollen fibres. Woollen fibres are then processed to obtain woollen yarn. Shearing does not hurt the sheep as the uppermost layer of the skin is dead.
• Step II: The sheared skin with hair is thoroughly washed in tanks to remove grease, dust and dirt. This is called scouring. Nowadays scouring is done by machines.
• Step III: After scouring, sorting is done. The hairy skin is sent to a factory where hair of different textures are separated or sorted.
• Step IV: The small fluffy fibres, called burrs, are picked out from the hair. The fibres are scoured again and dried. This is the wool ready to be drawn into fibres.
• Step V: The fibres can be dyed in various colours, as the natural fleece of sheep and goats is black, brown or white.
• Step VI: The fibres are straightened, combed and rolled into yarn. The longer fibres are made into wool for sweaters and the shorter fibres are spun and woven into woollen cloth.

34. Give a short note on Occupational hazards.
Answer:
Wool industry is an important means of livelihood for many people in our country. But sorter’s job is risky as sometimes they get infected by a bacterium, anthrax, which causes a fatal blood disease called sorter’s disease. Such risks faced by workers in any industry are called occupational hazards.

35. Define the word sericulture.
Answer:
The rearing of silkworms for obtaining silk is called sericulture.

36. Define the term ‘selective breeding’.
Answer:
The process of breeding of selective parents for obtaining special characters in their offspring such as soft under hair in sheep, is termed as selective breeding.

37. Sheep are herbivores, so which type of food is provided by rearers?
Answer:
Sheep are herbivores in which they prefer grass and leaves of various trees. Apart from grazing sheep, rearers also feed them on a mixture of pulses, corn, jowar, oil cakes (material left after taking out oil from seeds) and minerals. In winter, sheep are kept indoors and fed on leaves, grain and dry fodder.

38. Give some breeds of Indian sheep.
Answer:
Some breeds of Indian sheep are as follows:
• Lohi in Rajasthan and Punjab
• Rampur bushair in Uttar Pradesh, Himachal Pradesh
• Nali in Rajasthan, Haryana and Punjab
• Bakharwal in Jammu and Kashmir
• Marwari in Gujarat
• Patanwadi in Gujarat

39. Write a caption for each of the following figures as given in the figure (a-f).

Answer:
a) Adult male silk moth
b) Adult female silk moth
c) Eggs on mulberry leaves
d) Silkworms
e) Cocoons
f) Cocoons with developing moth

40. What is cocoon?
Answer:
The silky covering spun by the silkworm (or caterpillar) of silk moth is called cocoon.

41. Name the different types of silk.
Answer:
The different types of silk include
• Mulberry silk
• Tassar silk
• Eri silk
• Mooga silk
• Kosa silk

42. Which silk moth is most common?
Answer:
The most common silk moth is the mulberry silk moth.

43. Given below is a sequence of steps in the processing of wool. Which are the missing steps? Add them.
Shearing, __________, sorting, __________, __________, _________.
Answer:
Shearing, Scouring, sorting, picking of burrs, dying of fibres, making of yarn.

44. What do you know about discovery of silk?
Answer:
The exact time of discovery of silk is perhaps unknown. According to an old Chinese legend, the empress Si-lung-Chi was asked by the emperor Huang-ti to find the cause of the damaged leaves of mulberry trees growing in their garden. The empress found white worms eating up mulberry leaves. She also noticed that they were spinning shiny cocoons around them. Accidentally a cocoon dropped into her cup of tea and a tangle of delicate threads separated from the cocoon. Silk industry began in China and was kept a closely guarded secret for hundreds of years.

45. Write the difference between natural silk and artificial silk.
Answer:
Natural silk is obtained from the cocoons of silkworms and it is made up of a protein. Natural silk is an animal fibre. However, artificial silk is obtained from wood pulp and it is made up of modified plant material ‘cellulose’. If the natural silk fibre is burnt, it gives a smell of burning hair while if artificial fibre is burnt, it gives a smell of burning paper.

46. Steps for the production of silk are given below in a jumbled order. Arrange them in their proper sequence.
a) Eggs are warmed to a suitable temperature for the larvae to hatch from eggs.
b) Fibres are taken out from the cocoon.
c) After 25 to 30 days, the caterpillars stop eating and start spinning cocoons.
d) The larvae/caterpillars or silkworms are kept in clean trays along with freshly chopped mulberry leaves.
e) Female silk moths lay eggs.
f) Cocoons are kept under the sun or boiled in water.
Answer:
The correct order is
e) Female silk moths lay eggs.
a) Eggs are warmed to a suitable temperature for the larvae to hatch from eggs.
d) The larvae/caterpillars or silkworms are kept in clean trays along with freshly chopped mulberry leaves.
c) After 25 to 30 days, the caterpillars stop eating and start spinning cocoons.
f) Cocoons are kept under the sun or boiled in water.
g) Fibres are taken out from the cocoon.

47. Four different types of fibres are given to you. Out of these, two fibres (1 and 2) are obtained from plants and other two (3 and 4) fibres are obtained from animals. Fibre (1) is used in filling quilts and the yarn made of fibre (2) is used in making gunny bags. The yarn made from fibre (3) is used for knitting sweaters and yarn of fibre (4) is used for weaving saris. Name the four given fibres marked 1, 2, 3 and 4.
Answer:
Fibre (1) which is used in filling quilts is cotton and fibre (2) is jute. Fibre (3) is wool and fibre (4) which is used for weaving saris is silk.

48. Rama wanted to buy a silk frock and went to the market with her mother. There they found that the artificial silk was much cheaper and wanted to know why? Explain the reason.
Answer:
Artificial silk, the rayon, is obtained from wood pulp and is made of modified plant material cellulose. Synthetic silk can be prepared at a large scale in factories/mills and can be dyed in various colors easily. Therefore, it is cheap. On the other hand, for obtaining natural silk, we have to rear silk moth, their larvae to get pupa. To get silk thread, we have to dip cocoon in hot water to get silk thread which is wrapped over the cocoon. The pupa inside the cocoon dies. To obtain silk for commercial purposes, a large number of cocoons (containing living pupa) are killed. Therefore, natural silk is costly.

49. Describe the life history of silk moth.
Answer:
The female silk moth lays eggs, from which hatch larvae which are called caterpillars or silkworms. They grow in size and when the caterpillar is ready to enter the next stage of its life history called pupa, it first weaves a net to hold itself. Then it swings its head from side to side in the form of the figure of eight (8). During these movements of the head, the caterpillar secretes fibre made of a protein which hardens on exposure to air and becomes silk fibre. Soon the caterpillar completely covers itself by silk fibres and turns into pupa. This covering is known as cocoon. The further development of the pupa into moth continues inside the cocoon. Silk fibres are used for weaving silk cloth. The silk yarn (thread) is obtained from the cocoon of the silk moth. There is a variety of silk moths which look very different from one another and the silk yarn they yield is different in texture (coarse, smooth, shiny, etc.). Thus, tassar silk, mooga silk, kosa silk, etc., are obtained from cocoons spun by different types of moths. The most common silk moth is the mulberry silk moth. The silk fibre from the cocoon of this moth is soft, lustrous and elastic and can be dyed in beautiful colours.

50. How silkworms are reared? Explain in brief.
Answer:

• Rearing silkworms: A female silk moth lays hundreds of eggs at a time. The eggs are stored carefully on strips of cloth or paper and sold to silkworm farmers. The farmers keep eggs under hygienic conditions and under suitable conditions of temperature and humidity. The eggs are warmed to a suitable temperature for the larvae to hatch from eggs. This is done when mulberry trees bear a fresh crop of leaves. The larvae, called caterpillars or silkworms, eat day and night and increase enormously in size. The larvae are kept in clean bamboo trays along with freshly chopped mulberry leaves. After 25 to 30 days, the caterpillars stop eating and move to a tiny chamber of bamboo in the tray to spin cocoons. Small racks or twigs may be provided in the trays to which cocoons get attached. The caterpillar or silkworm spins the cocoon inside which develops the silk moth.
• Processing silk: A pile of cocoons is used for obtaining silk fibres. The cocoons are kept under the sun or boiled or exposed to steam. The silk fibres separate out. The process of taking out threads from the cocoon for use as silk is called reeling the silk. Reeling is done in special machines, which unwind the threads or fibres of silk from the cocoon. Silk fibres are then spun into silk threads, which are woven into silk cloth by weavers.

51. Neha went to the market with her mother to buy a silk saree for her grandmother. The shopkeeper was showing sarees of different varieties of silk but her mother wanted to take only a pure silk saree and not an artificial one. Neha was confused that how to distinguish between a pure silk and an artificial silk saree. But her mother helped her in selecting a pure silk saree for her grandmother and she was quite elated about that.
Answer the following questions that follow:
a) How Neha’s mother distinguished between pure silk saree and an artificial silk saree?
b) Is the pure silk saree more costly than an artificial one?
Answer:

a) Neha’s mother took a thread of natural silk fabric and another thread of artificial silk fabric and burnt them separately. The thread which burns giving a smell of burning hair is the natural silk while the thread which burns giving a smell a burning paper is the artificial silk.
b) Yes, pure silk saree is more costly than an artificial one because synthetic silk can be prepared at a large scale in factories/mills and can be dyed in various colors easily. Therefore, artificial silk is cheap.

Multiple Choice Questions
52. Llama and Alpaca are found in
a) South United States
b) South America
c) South China
d) South Russia
Answer:
b) South America

53. Which of the following animal does yield wool?
a) Dog
b) Cat
c) Alpaca
d) None of these
Answer:
c) Alpaca

54. Lohi breed of sheep is found in which of the following state?
a) Rajasthan
b) Gujarat
c) Himachal Pradesh
d) Uttar Pradesh
Answer:
a) Rajasthan

55. Nali breed of sheep is NOT found in which state?
a) Rajasthan
b) Himachal Pradesh
c) Haryana
d) Punjab
Answer:
b) Himachal Pradesh

56. Hair trap a lot of air as air is a __________ of heat.
a) Poor Conductor
b) Good Conductor
c) Option a) and b)
d) None of these
Answer:
a) Poor Conductor

57. The rearing of silkworms for obtaining silk is called
a) Cocoon
b) Silk
c) Sericulture
d) Silviculture
Answer:
c) sericulture

58. Which of the following is not a type of natural silk?
a) Mulberry Silk
b) Tassar Silk
c) Mooga Silk
d) Rayon
Answer:
d) Rayon

59. Paheli wanted to buy a gift made of animal fibre obtained without killing the animal. Which of the following would be the right gift for her to buy?
a) Woollen shawl
b) Silk scarf
c) Animal fur cap
d) Leather jacket
Answer:
a) Woollen shawl

60. Silk fibre is obtained from
a) fleece of sheep
b) bark of tree
c) cocoon
d) shiny jute stalk
Answer:
c) cocoon

61. Wool fibre cannot be obtained from which of the following?
a) Goat
b) Llama
c) Alpaca
d) Dog
Answer:
d) Dog

62. Selective breeding is a process of
a) selecting the offsprings with desired properties
b) selecting the parents with desired properties
c) selecting an area for breeding
d) selecting fine hair for good quality wool
Answer:
b) selecting the parents with desired properties

63. The general process that takes place at a sheep shearing shed is
a) removal of fleece
b) separating hair of different textures
c) washing of sheep fibre to remove grease
d) rolling of sheep fibre into yarn
Answer:
a) removal of fleece

64. Which of the following statement is correct?
a) In India, camels and goats are generally reared for obtaining wool.
b) The rearing of silkworms for obtaining silk is called silviculture.
c) In the process of obtaining wool from fleece, sorting is done after scouring.
d) Yak hair are not used to make woollen fabric.
Answer:
c) In the process of obtaining wool from fleece, sorting is done after scouring.

65. What is the scientific name of mulberry tree?
a) Magnifera indica
b) Morus Alba
c) Desmodium girence
d) None of these
Answer:
b) Morus Alba

66. The term sericulture is used for
a) making alcohol with the help of bacteria
b) rearing of silkworm
c) practicing farming
d) production of saree
Answer:
b) rearing of silkworm

67. Reeling of silk is
a) a process of making silk reels
b) spinning of silk fibres
c) weaving of silk cloth
d) the process of taking silk threads from cocoon
Answer:
d) the process of taking silk threads from cocoon

68. Which of the following statement is incorrect?
a) In the process, of obtaining wool from fleece, sorting is done after scouring.
b) The rearing of silkworms for obtaining silk and their rearing, breeding is called silviculture.
c) The small fluffy fibres are picked out from the hair, called burrs.
d) The longer fibres are made into wool for sweaters.
Answer:
b) The rearing of silkworms for obtaining silk and their rearing, breeding is called silviculture.

69. Silkworms secrete fibre made of
a) proteins
b) cellulose
c) protein
d) vitamin
Answer:
c) protein

70. Which of the following country is the largest producer of wool in the world?
a) Russia
b) Canada
c) Australia
d) Greenland
Answer:
c) Australia

71. Which country is the largest producer of silk in the world?
a) India
b) United States
c) China
d) France
Answer:
c) China

72. Which country produces fine quality of wool?
a) New Zealand
b) Germany
c) Sweden
d) Netherlands
Answer:
a) New Zealand

73. Which of the following not a natural fibre?
a) Silk
b) Cotton
c) Polyester
d) Wool
Answer:
c) Polyester

74. The maximum length of continuous silk thread that can be obtained from a cocoon is
a) 900 metres
b) 9000 metres
c) 90 metres
d) 900 centimetres
Answer:
a) 900 metres

75. The female silk moth lays eggs, from which hatch larvae which are called
a) butterfly
b) silkworms
c) mosquitos
d) None of these
Answer:
b) silkworms

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