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NCERT Class 7 Science Chapter 3 Fiber to Fabric
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Fiber to Fabric
Chapter: 3
NCERT TEXT BOOK EXERCISES
Q. 1. You must be familiar with the following nursery rhymes:
(i) Baa baa black sheep, have you any wool’.
(ii) ‘Mary had a little lamb, whose fleece was white as snow’.
Answer the following
(a) Which parts of the black sheep have wool?
Ans: The hair (fleece) of the black sheep have wool.
(b) What is meant by the white fleece of the lamb?
Ans: The white fleece is the white hair of the lamb.
Q. 2. The silk worm is:
(a) a caterpillar,
(b) a larva. Choose the correct option:
(i) (a)
(ii) (b)
(iii) both (a) and (b)
(iv) neither (a) nor (b).
Ans: (iii) Both (a) and (b).
Q. 3. Which of the following does not yield wool?
(i) Yak
(ii) Camel
(iii) Goat
(iv) Woolly dog.
Ans: (iv) Woolly dog.
Q. 4. What is meant by the following terms?
(i) Rearing.
Ans: The process of keeping, feeding, breeding and medical care of useful animals is called rearing of animals. These animals produce one or more useful products for human beings.
(ii) Shearing.
Ans: The fleece of the sheep along with a thin layer of skin is removed from its body. This process is called shearing.
(iii) Sericulture.
Ans: The rearing of silkworms for obtaining silk is called sericulture.
Q.5. Given below is a sequence of steps in the processing of wool. Which are the missing steps? Add them.
Shearing _______ sorting, _________, __________, ___________.
Ans: Shearing, scouring, sorting, drying, dyeing, spinning, weaving.
Q. 6. Make sketches of the two stages in the life history of the silk moth which are directly related to the production of silk.
Ans: Silkworm → Cocoon with pupa
Q. 7. Out of the fol! wing, which are the two terms related to silk production?
Sericulture, Floriculture, Moriculture, Apiculture, Silviculture.
Hints:
(i) Silk production involves cultivation of Mulberry leaves and rearing silkworms.
(ii) Scientific name of Mulberry is Morus alba.
Ans: (i) Sericulture.
(ii) Moriculture.
Q. 8. Match the words of Column I with those given in Column II:
| Column – I | Column – II |
| 1. Scouring | (a) Yields silk fibers |
| 2. Mulberry leaves | (b) Wool yielding animal |
| 3. Yak | (c) Food of silk worm |
| 4. Cocoon | (d) Reeling(e) Cleaning sheared skin |
Ans:
| Column – I | Column – II |
| 1. Scouring | (e) Cleaning sheared skin |
| 2. Mulberry leaves | (c) Food of silk worm |
| 3. Yak | (b) Wool yielding animal |
| 4. Cocoon | (a) Yields silk fibers |
Q.9. Given below is a cross word puzzle based on this lesson. Use hints to fill in the blank spaces with letters that complete the words:
| Down | Acros |
| 1. Thorough washing | 1. Keep warm |
| 2. Animal fiber | 2. Its leaves are eaten by silkworms |
| 3. Long thread like structure | 3. Hatches from egg of moth |
Ans:
ADDITIONAL IMPORTANT QUESTIONS
Very Short Answer Questions
Q. 1. What do you mean by the rearing of animals?
Ans: The keeping and feeding of animals is called rearing of animals.
Q. 2. What is the aim of rearing sheep?
Ans: The main aim to rear the sheep is to obtain wool.
Q. 3. What is shearing?
Ans: The process of removing hair (or cutting off hair) from the body of a sheep in the form of fleece is called shearing.
Q. 4. What do you know about sorting?
Ans: The process of separating the fleece of a sheep into sections according to the quality of woollen fibers (such as fine, coarse, long, short etc.) is called sorting.
Q. 5. What is scouring?
Ans: The process of washing the fleece (cut hair of sheep) that removes dust, dirt, dried sweat and grease is called scouring.
Q. 6. From which animal, the silk is obtained?
Ans: Silk moth.
Q. 7. What is sericulture?
Ans: The rearing of silkworms for obtaining silk is called sericulture.
Q. 8. In which stage the silk moth spins the silk fiber around itself?
Ans: Caterpillar.
Q. 9. What is cocoon?
Ans: The silky covering spun by the silk worm (or caterpillar) of silk moth is called Cocoon.
Q. 10. Define the term reeling the silk.
Ans: The process of taking out silk fibers from the cocoons for use as silk is called reeling. Reeling is done in special machines which unwind the fibers of silk from cocoons.
Q. 11. Which step comes first in the production of woolen yarn from sheep: scouring or shearing?
Ans: Shearing.
Q. 12. Which stage comes earlier in the life history of a silk-moth: pupa or larva?
Ans: Larva.
Q. 13. State whether artificial silk is an animal fiber or a plant fiber.
Ans: Plant fiber.
Q.14. Name the plant on which silk larva feeds.
Ans: Silk larva feeds on the leaves of mulberry tree.
Q. 15. What is the life span of a silk moth?
Ans: 3-4 days.
Short Answer Questions
Q. 1. State two uses of silk.
Ans: (i) It is used for making clothes (sarees, scarves, dresses etc).
(ii) It is used in parachutes, bullet proof nests.
Q.2. What type of feed (or food) is given to sheep?
Ans: Sheep are herbivores and prefer leaves and grass. The wool-yielding sheep are given protein rich food such as mixture of corn, pulses, jowar and oil-cake.
Q.3. The hair of an animal A are cut from its body in one piece along with a thin layer of its skin in the form of B. This process is called C. The B of this animal is then cleaned by using soap and a lot of water by a process D. The clean B is then converted into yarn E by the process of sorting, dyeing, combing and spinning.
(a) What could be:
(i) A and
(ii) B?
Ans: (i) Sheep.
(ii) Fleece.
(b) Name the process
(i) C and
(ii) D.
Ans: (i) Shearing.
(ii) Scouring.
Q. 4. P, Q, R and S are all various types of fibers. The fibers P and Q are obtained from animals, whereas the fibers R and S are obtained from plants. The yarn made from P is used for knitting sweaters whereas the yarn made from Q is used for weaving saris. The fiber R is used in filling quilts whereas the yarn made of fiber Qis used in making gunny bags. What are P, Q, Rand S?
Ans: P is wool, Q is silk, R is cotton, S is Jute.
Q. 5. A is an insect which looks like a butterfly. A is not formed as such from its eggs directly. The hatching of eggs produces a stage called B or C, and then an encased form D which ultimately forms insect A. The worm-like stage B or C is also known by a yet another name E. The E is important because it leads to the formation of an important fiber F.
(a) Name the insect A.
Ans: Silk moth.
(b) What are stages:
(i) B
(ii) C?
Ans: (i) larva.
(ii) caterpillar.
Q. 6. Write any two health hazards faced by workers in sericulture and wool production.
Ans: (i) Handling of dead silk worms with bare hands may lead to infection and illness.
(ii) One of the serious health hazards for workers in the wool production industry is exposure to a type of bacteria called anthrax. It causes a disease called wool sorter’s disease.
Q. 7. Explain the process to obtain silk thread from cocoon.
Ans: Cocoons are kept under the sun or boiled to or exposed to steam. The silk fibers separate out. This process of obtaining silk from the cocoons is called reeling the silk. Reeling is done in special machines.
Q. 8. What is shearing? Why shearing does not cause any pain to the sheep?
Ans: The process of shaving off a sheep’s body to obtain fleece along with a thin layer of skin is called shearing.
Shearing does not cause any pain to the sheep because the uppermost thin layer of their skin is dead.
Q. 9. Why the hair of the body of sheep keep them warm during colder conditions?
Ans: Wool fiber is highly porous. The air in the pores acts as an insulator and does not allow the body heat to go out. Thus, hair on the body of sheep keep them warm during colder conditions.
Q. 10. What happens when the silk caterpillar stops feeding?
Ans: When the silk caterpillar stops feeding, its salivary gland starts secreting a sticky fluid (a protein called fibroin). This fluid hardens on exposure to air and forms a long thread of silk. This thread gets wrapped around its body to form a ball-like structure called cocoon.
Short Answer Questions
Q. 1. Some animals have a thick coat of hair on their body. These hair give a material X which is used for making cardigans after suitable treatment. The material X traps a lot of Y which prevents the body heat of these animals from being lost to surroundings and keeps them warm in winter. The material X is removed from the animals at the beginning of the season Z.
(a) What are:
(i) X and
(ii) Y?
Ans: (i) Wool.
(ii) Air.
(b) Name the season Z.
Ans: Summer.
(c) Name any four animals which yield X.
Ans: Sheep, Goat, Yak, Camel.
Q. 2. Define the following:
(i) Throwing.
(ii) Shoddy.
(iii) Roving.
Ans: (i) Throwing: The process of twisting one or more silk threads to make sufficiently strong silk stands fit for weaving or knitting is known throwing.
(ii) Shoddy: The fabrics made from the used wool by carding, spinning and weaving is called shoddy.
(iii) Roving: The splitting of woollen web into fine thin strands for spinning is known as Roving.
Q. 3. What treatment is given to the sheared hair of sheep in:
(i) Scouring
(ii) Sorting. and
(iii) Carding?
Ans: (i) Scouring: In scouring, the sheared skin with hair is thoroughly washed in soap solution in a number of tanks to remove grease, dirt and dust.
(ii) Sorting: In sorting the dried hair of different textures are sorted out. The small fluffy fibers called burrs are picked out and sent for reprocessing.
(iii) Carding: In carding process, selected curly wool fibers are straightened by passing through rollers.
Q. 4. How silk fibers of different textures are prepared?
Ans: The silk yarn 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 like coarse, smooth and shiny, etc. Thus, tassar silk, mooga silk and kosa silk are obtained from cocoons spun by different types of moths. The most common silk moth is. the mulberry silk moth.
Q. 5. Explain the processing of cocoons to obtain silk fibres.
Ans: All the cocoons are collected at one place. The pile of cocoons is used for obtaining silk fibres. The pile of cocoons is placed in hot water. Hot water makes the silk fibres of cocoons to separate out. The long silk fibres are obtained by unwinding the threads from cocoons. The process of taking out silk fibres from the cocoons for use as silk is called reeling. Reeling is done in special machine which unwind the fibres of silk from cocoons.
Long Answer Type Questions
Q. 1. Explain the steps involved in wool production.
Ans: The steps involved in wool production are as follows:
Step I. Shearing: The process of removal of the woolen coat or fleece from the animal is called shearing. This is done without harming the animal by using shearing tools.
Step II. Scouring: Washing the sheared wool in hot water and detergent and then drying it is called scouring. This is done to remove dirt, dust and grease from the wool.
Step III. Sorting: The process of removing any stained, damaged, and inferior wool from the fleece is called sorting. Burrs, which are soft fluffy fibres in wool, are picked out from the hair.
Step IV. Grading: The process of sorting the wool according to the length, colour, and texture of fibres is called grading.
Step V. Dyeing: The natural hair of sheep is white, brown or black. The hair is dyed with different colours for commercial use.
Step VI. Making yarn: The wool is passed through rollers and combed into sheets with the help of a machine called a carding machine. The sheet is then twisted into a rope called sliver. The sliver is stretched and twisted into a thin yarn.
Q. 2. Explain the rearing of silk worms to obtain cocoons.
Ans: A female silk moth lays hundreds of eggs at a time [Fig. 3.10(a)]. The eggs of silk moths are stored carefully on paper strips (or cloth strips) and sold to silkworm farmers. The farmers keep these eggs at suitable temperature and humidity under hygienic conditions. The eggs are then warmed to a suitable temperature for hatching. When the eggs hatch, silkworms (larvae or caterpillars) come out of eggs.
Fig. 3.10. Production of silk
The silkworms are fed cut-up mulberry leaves [Fig. 3.10(6)] The silkworms eat day and night and grow big in size. After about 25 to 30 days, the silkworms stop eating and get ready to spin cocoons, The silkworms climb the twigs placed near them and spin cocoons of silk fibres. The silkworms enclose themselves completely inside the silken cocoons in two or three days [Fig. 3.10(c)]
HOTS QUESTIONS
Q. 1. (a) How many silkworms are required to produce one kilogram of raw silk?
(a) Name the sticky fluid secreted by larva (caterpillar) from its salivary glands.
Ans: (a) About 5500 silk worms are required to produce one kilogram of raw silk.
(b) The sticky fluid secreted by larva (caterpillar) is called fibroin.
Q.2. Name the feature that determines the quality of wool.
Ans: The quality of wool is determined on the basis of thickness, texture, length, shine, strength and color of the fiber..
Q.3. The moth A lays hundreds of eggs. The eggs hatch to produce worms B which are fed cut-up leaves of tree C. After about 25 to 30 days the worms stop eating and spin cocoons of fibers D. The fibers D are separated from cocoons by the process E. The spinning of these fibers produce a yarn which is woven on looms into fine cloth used for making saris, etc.
(a) What is moth “A”?
Ans: (a) Silk moth.
(b) Name
(i) worm B. and
(ii) tree C.
Ans: (i) Silk worm.
(ii) Mulberry tree.
(c) What are fibers D?
Ans: Silk.
(d) Name the process E
Ans: Reeling.
SKILL BASED QUESTIONS
1. (a) Draw a labeled diagram to show the rearing of silk worms.
(b) What is the use of mulberry tree?
(e) Write the other name of silkworms.
(b) The silkworms eat the mulberry leaves.
(c) The other name of silkworm is caterpillar.
2. Identify the following animals and name the type of wool obtained from them:
Ans: Fig (a) is yak.
Fig (b) is camel.
The hair of yak are used to make yak wool.
The hair of camels are used to make wool called fur.
FORMATIVE ASSESSMENT
1. Fill in the following blanks with suitable words:
(i) The process of selecting parents for obtaining special characteristics in their off springs is called selective __________.
Ans: Breeding.
(ii) Angora wool is obtained from Angora _________.
Ans: Goat.
(iii) Llama and alpaca also yield ________.
Ans: Wool.
(iv) Sheep are ________ and prefer grass and leaves.
Ans: Herbivores.
(v) Lohi and nali are the breeds of ______.
Ans: Sheep.
(vi) Silk is obtained from the _________ of the silk moth.
Ans: Cocoon.
(vii) Silk fibers are made of a _________.
Ans: Protein.
(viii) Silk worms are _________ of silk moth.
Ans: Larvae (or caterpillars).
(ix) Silk worms spin _______ of silk fibers.
Ans: Cocoon.
(x) The process of taking out threads from the cocoons for use as silk is called _________ the silk.
Ans: Reeling.
2. State whether the following statements are true or false:
(i) The adult silk moth spins cocoons from which silk is obtained.
Ans: False.
(ii) The silk worm is a caterpillar as well as larva.
Ans: True.
(iii) The wool of sheep is removed only once a year before the beginning of rainy season.
Ans: False.
(iv) Rampur bushair and Bakharwal are the breeds of sheep.
Ans: True.
(v) Sorter’s disease is caused by virus.
Ans: False.
(vi) The rearing of silkworms for obtaining silk is called sericulture.
Ans: True.
(vii) Silk fiber is obtained from eggs of silk moth.
Ans: False.
(viii) Fully grown cocoons are sorted out on the basis of their color.
Ans: False.
(ix) After shearing, the sheep is exposed to sun rays.
Ans: False.
(x) During scouring, the sheared hair are washed with soap solution.
Ans: True.
3. Match the items of column A with those given in column B:
| Column – A | Column – B |
| 1. A variety of wild silk having a golden yellow color. | (a) Merino |
| 2. Science of rearing silk worms so as to obtain silk. | (b) Muga |
| 3. The name of sheep which produces finest variety of wool. | (c) Sericulture |
| 4. An international trade mark for new and pure wool. | (d) Worsted |
| 5. A woolen fabric having a smooth surface. | (e) Woolmark |
Ans:
| Column – A | Column – B |
| 1. A variety of wild silk having a golden yellow color. | (b) Muga |
| 2. Science of rearing silk worms so as to obtain silk. | (c) Sericulture |
| 3. The name of sheep which produces finest variety of wool. | (a) Merino |
| 4. An international trade mark for new and pure wool. | (e) Woolmark |
| 5. A woolen fabric having a smooth surface. | (d) Worsted |
4. Write one word for the following:
(i) The process of shaving off a sheep’s body to obtain fleece.
Ans: Shearing.
(ii) Rearing of silk moth.
Ans: Sericulture.
(iii) The process by which curly wool fibers are straightened.
Ans: Carding.
(iv) Washing of sheared skin with hair of a sheep.
Ans: Scouring.
(v) The sticky fluid which on exposure to air forms a thread of silk.
Ans: Fibroin.
(vi) The thick coat of hair on a sheep’s body.
Ans: Fleece.
(vii) The process of shedding skin.
Ans: Moulting.
(viii) A silky case spun by the caterpillar of silk worm around its body.
Ans: Cocoon.
(ix) Spun thread used for knitting, weaving or sewing.
Ans: Yarn.
(x) A natural protein fibre which is strong, hard, lustrous and obtained from Cocoons.
Ans: Silk.
5. Multiple Choice Questions:
(i) The rearing of silk worms for the production of silk is known as:
(a) apiculture
(b) silviculture
(c) pisciculture
(d) sericulture
Ans: (d) Sericulture.
(ii) The caterpillars of silk worms feed on:
(a) rose leaves
(b) mulberry leaves
(c) teak leaves
(d) grass
Ans: (b) Mulberry leaves.
(iii) The process of taking out silk threads from the cocoon is called:
(a) reeling
(b) rearing
(c) sorting
(d) grading
Ans: (a) Reeling.
(iv) Which of the following animals does not yield wool?
(a) sheep
(b) yak
(c) alpaca
(d) snake
Ans: (d) Snake.
(v) The process of removal of fleece from the body of sheep is called:
(a) cleaning
(b) carding
(c) shearing
(d) reeling
Ans: (c) Shearing.
(vi) Silk thread is obtained from:
(a) adult moth
(b) pupa
(c) caterpillar
(d) cocoon
Ans: (d) Cocoon.
(vii) Which one of the following is not an example of natural fiber?
(a) silk
(b) rayon
(c) cotton
(d) wool
Ans: (b) Rayon.
(viii) The silk and wool are made of a kind of:
(a) fats
(b) carbohydrates
(c) proteins
(d) vitamins
Ans: (c) Proteins.
(ix) Silk worm is called:
(a) adult silk moth
(b) female silk moth
(c) caterpillar
(d) pupa
Ans: (c) Caterpillar.
(x) We can obtain wool from:
(a) goat
(b) yak
(c) sheep
(d) all of the above
Ans: (d) All of the above.
