NCERT Class VII Science Solution: Chapter 3-Fibre to Fabric Part 5

Download PDF of This Page (Size: 384K)

LONG ANSWER QUESTIONS

Question 21:

Complete the paragraph related to the life history of silk moth by filling in the blanks.

The__________ silk moth lays__________ from which hatch__________ called__________ or__________. They grow in size and when the caterpillar is ready to enter the next stage of its life history called__________, it first weaves a covering to hold itself, which is known as__________.

Answer:

The female silk moth lays eggs from which hatch larvae 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 covering to hold itself, which is known as 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:

The thread which bums with a smell of burning hair is from pure silk. Silk and hair are protein fibres. 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:

Fabric needs more energy to tear apart as compared to a single fibre.

Question 24:

Write various steps for processing fibres into wool.

Answer:

Write briefly about

  1. Shearing

  2. Scouring

  3. Sorting

  4. picking out of burrs from the hair

  5. Dyeing of fibres

  6. Straightening, combing of fibres and rolling into yarm.

Image of various steps for processing fibres into wool

Image of Various Steps for Processing Fibres into Wool

Image of various steps for processing fibres into wool

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.

Image of various stage of silk moth

Image of Various Stage of Silk Moth

Image of various stage of silk moth

The female silk moth lays eggs on the leaves of a mulberry tree. The eggs hatch to form larvae called ‘caterpillar’ or ‘Silkworms’. The silkworm 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.