NCERT Exemplar Problems Class 7 Science – Fibre to Fabric

Question 1:
The rearing of silkworms for obtaining silk is called
(a) cocoon
(b) silk
(c) sericulture .
(d) silviculture
Answer:
(c) Sericulture is a practice of rearing silkworms for obtaining silk while silviculture is a practice of developing and caring forests

Question 2:
Which of the following is not a type of silk?
(a) Mulberry silk
(b) Tassarsilk
(c) Mooga silk
(d) Moth silk
Answer:
(d) Moth is the silkworm under development inside a cocoon. Mulberry, Tassar and Mooga are varieties of silk produced by different rearing practices.

Question 3:
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) Rest of the options given here are obtained by killing animals, but wool is produced from shearing of skin of sheep.

Question 4:
Silk fibre is obtained from
(a) fleece of sheep
(b) cotton ball
(c) cocoon
(d) shiny jute stal
Answer:
(c) Cocoon is one of the stage of life cycle of silkworm. Fleece of sheep gives wool, cotton ball gives cotton and jute stalk gives jute fibre.

Question 5:
Wool fibre cannot be obtained from which of the following?
(a) Goat
(b) Llama
(c) Alpaca
(d) Moth
Answer:
(d) Moth is an insect while other three are the animals with fur which produce wool.

Question 6:
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) hen certain desired traits (properties) of parents are considered before breeding, it is called selective breeding.

Question 7:
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 is called sheep shearing, separating hair of different textures is called sorting, washing wool to remove grease is called scouring and rolling of sheep fibre into yarn is called rolling.

Question 8:
The term sericulture is used for
(a) culture of bacteria
(b) rearing of silkworm
(c) making silk fabric from silk yarn
(d) production of sarees
Answer:
(b) Sericulture is the rearing of silkworm to obtain silk fibre. Sericulture means ‘silk farming’.

Question 9:
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) Reeling of silk is the process of taking out threads from the cocoon for use as silk

Question 10:
Silkworms secrete fibre made of
(a) fat
(b) cellulose
(c) protein
(d) nylon
Answer:
(c) Silk protein consists of sericin and fibroin mainly. Fat and cellulose are not present in silk. Nylon is a synthetic fibre.

Very Short Answer Type Questions

Question 11:
Fill in the blanks in the following statements.
(a) and________ fibres are obtained from animals.
(b) Silk fibres come from________ of silk_________ .
(c) Wool yielding animals bear________ on their body.
(d) Hair trap a lot of________ which is a poor_________ of heat.
Answer:
(a) Silk, wool
(b) cocoon, worm
(c) fleece (hair)
(d) air, conductor

Question 12:
State whether the following statements are True or False. If false, correct them.
(a) Silkworms are caterpillars of silk moth.
(b)In India, camels and goats are generally reared for obtaining wool.
(c) The rearing of silkworms for obtaining silk is called silviculture.
(d) In the process of obtaining wool from fleece, sorting is done after scouring.
(e) Yak hair are not used to make woollen fabric.
Answer:
(a) True
(b) False, sheep are mostly reared for wool in India.
(c) False, it is called sericulture, silviculture is caring and developing forests.
(d) True
(e) False, wool can be made from sheep, yak, llama, camel, alpaca and goats.

Question 13:
How do the hair of certain animals help in keeping their bodies warm?
Answer:
Hair (or wool) of these animals trap a lot of air. Air is a poor conductor of heat. So, the air trapped in hair (or wool) of these animals prevents their body heat from being lost to cold surroundings and keeps them warm.

Short Answer Type Questions

Question 14:
Match the items of Column I with the items given in Column II.

Answer:
The correct matching is as given (a)—(iii), (b)—(iv), (c)—(ii), (d)—(i)
Note Yak are found in Tibet and Ladakh, while angora goats are reared in Jammu and Kashmir. Mulberry leaves are used to feed silkworm. Scouring is the process to clean sheared hair.

Question 15:
Various steps involved to obtain wool from fleece are given here.
(a) Picking out the burrs
(b) Dyeing in various colours
(c) Shearing
(d) Scouring
(e) Sorting
Write the above steps in the correct sequence in which they are carried out.
Answer:
The correct sequence is
Shearing —>Scouring —> Sorting —> Picking out the burrs —> Dyeing in various colours

Question 16:
Some words related with silk are jumbled up. Write them in their correct form.
(a) TURECULRISE
(b) WILSMORK
(c) BELMURRY
(d) RIN6LEE
Answer:
(a) SERICULTURE
(b) SILKWORM
(c) MULBERRY
(d) REELING

Question 17:
Figure shows three rings of circles with letters in them. Some of these letters in each ring can form the name of one wool yielding animal. Find the names of these animals.

Answer:
These animals are yak, camel and sheep.

Question 18:
Write a caption for each of the figure given as figure (a-d).

Answer:
(a) Eggs of silk moth on mulberry leaf
(b) Silkworm
(c) Cocoon
(d) Cocoon with developing moth

Question 19:
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.
(e) 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.
(a) After 25 to 30 days, the caterpillars stop eating and start spinning cocoons.
(f) Cocoons are kept under the sun or boiled in water.
(b) Fibres are taken out from the cocoon.

Question 20:
A wholesale woollen fibre dealer gets the woollen fibre of different textures sorted for various purposes. Match the items in Column I with the woollen fibre in Column II.

Answer:
The correct matching is as given
(a)—(iii), (b)—(i), (c)—(ii), (d)—(iv)

Long Answer Type Questions

Question 21:
Complete the paragraph related to the life history of silk moth by filling in the blanks.
The (a)……… silk moth lays (b)……… from which hatch (c)……….. called
(d)…… or (e)……….. They grow in size and when the caterpillar is ready to enter the next stage of its life history called (f)……………. It first weaves a covering to hold itself which is known as (g)…………..
Answer:
(a) female (b) eggs (c) larvae (d) caterpillars (e) silkworm (f) pupa (g) cocoon

Question 22:
Paheli went to the market to buy sarees for her mother. She took out a thread from the edge of the two sarees shown by the shopkeeper and burnt them. One thread burnt with a smell of burning hair and the other burnt with the smell of burning paper. Which thread is from a pure cotton saree and which one from a pure silk saree? Give reason for your answer.
Answer:
In first saree, one thread which burnt with a smell of burning hair is from pure silk, silk and hair are protein fibres. So, on burning these threads, a smell of burning hair comes out. In second saree, second thread which burnt with the smell of burning paper is from a cotton saree.
Since, cotton and paper both are carbohydrates and on burning, they give similar smell.

Question 23:
Explain the phrase – ‘Unity is Strength’ on the basis of the making of fabric from fibre.
Answer:
Fibres and fabric play a large role in everyday applications. A fibre is a hair-like strand of material. They are the smallest visible unit of a fabric and denoted by being extremely long in relation to their width. Fibres can be spun into yarn and made into fabric.
A single fibre is too weak to break but when some fibres together make a fabric, it is difficult to tear. Fabric needs more energy to tear apart as compared to a single fibre.

Question 24:
Write various steps for processing fibres into wool.
Answer:
The various steps for processing fibres into wool are as follows:
(i) Shearing The first step is to remove fleece of the sheep along with thin layer of skin. This process is called shearing.
(ii) Scouring In this step, the sheared hair is washed thoroughly to remove grease, dust and dirt.
(iii) Sorting In this step, different textures of hair are separated or sorted.
(iv) Separating burrs Burrs are small fluffy fibres which are picked out from the hair.
(v) Dyeing The fibres are dyed in various colours, as the original colours of fleece are usually black, white or brown.
(vi) Rolling In this process, the fibres are straightened, combed and rolled into yarn. And the fibres now as wool are ready to be woven.

Question 25:
Describe the life history of silk moth with the help of figures of various stages.
Answer:
The life cycle of silk moth is completed in four main stages as depicted below in the diagram:

The female silk moth lays eggs on the leaves of a mulberry tree. The eggs hatch to form larvae called ‘caterpillar’ or ‘silkworms’. The silkworms grow in size feeding on mulberry leaves and when the caterpillar is ready to enter the next stage of its life history called pupa, it first weaves a covering to hold itself, which is known as cocoon.
Pupa develop inside cocoon into moth and comes out as an adult male or female silk moth.