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NCERT Revision notes for class 7 Science Fibre to fabric

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Fibre: Fibres are the thin, thread-like strands that are used to make fabrics.

Fabric: Fabrics are the plain clothes, which are made using fibres.

Sericulture: The rearing of silkworm to obtain silk is called sericulture.

Types of fibres

There are two types of fibres:

  1. Natural fibres
  2. Synthetic fibres

1. Natural fibres: The fibres obtained from plants and animals are called natural fibre. Example: wool, silk and cotton.

2. Synthetic fibres: The fibres that are made in the lab using chemicals are called synthetic fibres. Example: polyster, nylon and rayon.

Steps involved in processing of fibres into wool

Step 1: Shearing

In this step, the fleece of the sheep is removed from its body with the help of machines.  

Step 2: Scouring

In this step, the sheared hair of the Sheep is washed in tanks to remove grease, dust and dirt.

Step 3: Sorting

In this step, the washed hair of sheep is sent to the factory where hairs of different textures are separated.

Step 4: Cleaning of burrs

In this step, the small fluffy fibres are picked from the hair. Then fibres are scoured again. And the wool become fit to be drawn into fibres.

Step 5: Dyeing

In this step, the fibres are dyed in various colours.

Step 6: reeling of silk

In this last step the fibres are straightened combed and rolled into yarn. Now this fibre can be used to to make sweater or other woollen clothes.

Life cycle of silk moth

  1. The female silk moth lays eggs.
  2. When the eggs are hatched, caterpillar came out of it.
  3. For 25 to 30 days, the caterpillar eat the mulberry leaves.
  4. After, that caterpillar is ready to enter its next life stage which is called pupa.
  5. First, the caterpillar weaves net to hold itself.
  6. The net covering of pupa is known as cocoon.

From cocoon to silk

  1. The female silk moth lays hundreds of eggs. These eggs are stored on strip of cloth or paper.
  2. When the egg hatches, larvae came out of it. These larvae are called caterpillar.
  3. The caterpillar eats mulberry leaves for 25 to 30 days.
  4. After the caterpillar stops eating leaves. It weaves net around it to form cocoon.
  5. These cocoons are then used to obtain silk.
  6. The cocoons are poured into a container of hot water where the silk is separated out of it.
  7. The thread taken out of cocoons is called reeling of silk.

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