Fibre to Fabric Complete Question Answers 2023 | SCIENCE (MY EUREKA PLUS) ,CLASS 7, CHAPTER 3 SOLUTIONS

II. 1. It absorb good amount of moisture without becoming damp .

Ans: Wool.

2. It is secreted by a caterpillar.

Ans: Silk.

3. It is flame resistant.

Ans: Wool.

4. It is the most popular fabric for tailoring fine garments.

 Ans: Woollen fabric .

5. It can be dyed easily and is very elastic.

Ans: Silk. 

III. 1. What is Cashmere wool?

Ans: The wool obtained from the Cashmere goats found in the Kashmir region is called Cashmere wool . 

2. What is camel wool used for?

Ans : The camel wool is used for making coats , robes and sportswear. 

3. What is sericulture?

Ans: The controlled production of silk from silk moth ,caterpillars is known as sericulture.

4. Why cannot a single silk fibre form a thread?

Ans: The fibre of a single cocoon is too fine to handle as a result of which  a single silk fibre cannot form a thread.

5. What is shearing?

Ans: Shearing is the first step in the  processing of wool.

IV. 1. Mention two characteristics of wool fibre.

Ans:  The two characteristics of wool fibre are –

           a) Wool is elastic and returns to its original position after being stretched.

             b) Wool absorbs good amount of  moisture (water) without getting damp. 

 2. List the steps  in wool processing .

Ans: The steps in wool processing are as follows-

          a) Shearing 

          b) Washing 

          c) Drying 

          d) Dyeing ( adding colour)

          e) Slivering 

          f) Roving

         g) Spinning 

         h) Woven or Knitted .

3. Name two wild varities of wild silk worm.

 Ans: Eri and Muga are two wild varities of wild silk worm.

4. How do the farmers come to know that a silkworm is ready to spin a cocoon?

Ans: When the caterpillars stop eating at the end of the growth stage ,farmers knew that a silkworm is ready to spin a cocoon .

5. Why do the farmer keep silk moth’s eggs in warm and humid conditions ?

Ans: Farmers keep silk moth’s egg in warm and humid conditions for the eggs to hatch successfully.

6. What are the health hazards of silk production?

Ans:  The health hazards of silk production are –

              a) Fumes produced during boiling of the cocoons lead to respiratory diseases.

               b) Constant noise of machines and long working hours lead to headaches and backpain.

V. 1. Explain how wool yarn is produced from the fleece of sheep.

Ans: The steps are as follows-

       a) Shearing – It is the first step where fleece is peeled off in one place.

      b) Washing – It is the second  step where the raw fleece is washed to remove grease , vegetable matter and other impurities and is done by a process called scouring. 

      c)  Drying –  The raw wool is then squeezed and dried by passing it through a series of dryers.

     d) Dyeing – The wool is then dyed using different colours.

     e) Slivering – The fibres are then rolled over onto one another  into  fine strands called slivers.

      f) Roving – The fine strands are then twisted into rope like strands by process of roving.

     g) Spinning – The strands are then combed and prepared for spinning into wool yarn.

     h) Woven or Knitted – Wool is then either woven or knitted into garments.

2. What are the characteristics  of silk fibre?

Ans: The characteristics of wool fibre are –

          a) Silk is extremely elastic,the smoothest and finest of all fibres.

          b) It can be dyed easily and takes the highest lusture.

          c) It is the strongest natural fibre. 

          d) It can be stretched to  almost 25% of its original length.

3. How will you distinguish wool from cotton fibre?

 Ans:             WOOL                                                                                              COTTON

          a) When burnt it gives a sooty flame                              a) When burnt it leaves behind ash 

           and an unpleasant odour of burning hair.                        and gives odour of burning paper.

         b) It is an animal fibre.                                                    b) It is a plant fibre.

        c) The residue of burnt wool is hard.                                c) The residue of burnt cotton is soft.

4. How is silk extracted from cocoons?

Ans: Cocoons are the protein fibres stretched by the pupae. This cocoons after a close observation are put in boiling water to obtain  fibre which is then wound into a thread by sorting their size, colour and texture. The raw silk threads then undergo a series of processes like rolling ,warping  and twisting before being woven into a fabric. 

5. Explain the life cycle of silk moth.

Ans: The various stages in the life cycle of silk moth are as follows –

       a) Egg  –  The female silk moth lays large number of eggs and it gets fertile in about two weeks which later hatch into larvae.

       b) Larvae – The larvae after hatching grow large in size as they feed vigorously on fresh mulberry leaves . During this stage they shed their skin four times. 

      c) Pupa – The stage when caterpillars are about a month old and stop eating is called the pupal stage. The pupae now secrete protein fibres around them which hardens on exposure to air and form cocoons.

     d) Moth –  The caterpillars now develop in cocoons which are around 1 km long and are called moths . They live only for a few days after coming out of the cocoons and are unable to fly. 

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