CBSE Class 7 Science Notes Chapter 3 Fibre to Fabric

Learn from School Connect Online in this chapter we will learn about Fibres which are very thin, thread-like strands from which fabrics (or cloths) are made. Some examples of fibres are cotton, wool, silk, flax, jute, nylon, polyester and polyacrylic.Fibre to Fabric Class 7 Notes Science Chapter 3

The different topics covered in CBSE Class 7 Science Chapter 3 are tabulated below:

Ex. 3.1 – Wool

Fibres from Plants

• Plant fibre is mainly composed of cellulose and cellulose fibres. These are most commonly used to make paper and cloth.
• Cellulose generates long, often highly lustrous fibres when prepared appropriately.
• Plants including cotton, jute, flax and hemp are used to obtain plant fibres.

Jute

• Jute fibre is obtained only from the stem of the jute plants. It is soft, shiny and long fibre with a silky texture, which is grown in rainy season.
• Jute mainly grows in regions having alluvial soil which is found in the delta regions of the Ganges and Brahmaputra rivers.

Basics of Fabric

Fibres

• The finer part of the thread is referred to as fibre.
• Fibre is a thread like structure that is spun into ropes, clothes and strings.
• Fabrics are made from fibres obtained from natural or artificial sources. Example: rayon, nylon, polyester, etc.

Fibre to Yarn to Fabric

Fabric consists of thin strands called yarn, which in turn consists of thinner strands called fibres.

Cotton and Its Processing

• Cotton is obtained from cotton bolls, which are directly from the surface of cotton seeds.
• It is grown in black clayey soil with a warm climate.
• The processing of cotton involves Ginning, Spinning, Weaving and Knitting.

Fibre from Animals

Wool

• The natural animal fibre obtained from sheep, goat, yak, camel, etc.
• All these animals have an outer covering of hair, which is shaved off to obtain wool fibres.

Natural protein fibre is cultivated from the cocoon of mulberry silkworm larvae.

Wool from Animals

• Wool comes from sheep, goat, yak and some other animals. These wool-yielding animals bear hair on their body because hair keeps them warm and wool is derived from these hairy fibres.
• Wool is used to make various wool fabrics like woollen clothes, carpets, woollen sweaters, saddle cloths etc.

Rearing and Breeding of Sheep for Wool

Rearing: It is a process of breeding, feeding and providing medical care to sheep. These animals are kept since they produce one or more useful products for human beings.

Breeding: Some special breeds of sheep are specially chosen to give birth to sheep which have only soft under hair. This process of selecting parents for obtaining special characters in their offspring is termed as ‘selective breeding’.

Mary Had a Little Lamb

Processing fibres into wool

The skin of the sheep is hairy having two types of fibres forming its fleece:

(i) the coarse beard hair

(ii) the fine soft under-hair near the skin is the fleece.

This fleece is the main source of fibres of wool.

The process of making fibre into wool follows a series of processes: Shearing → Scouring → Sorting → Dyeing → Straightening, Rolling and Combing.

Occupational hazards of fibre production

Sometimes the sorters get infected by a bacterium, anthrax, which causes a fatal blood disease called sorter’s disease.

Ex. 3.2 – Silk

Silk from Animals

• Silk is a natural protein fibre which is obtained from silkworm and can be used as a textile fibre.
• The different types of silk are produced by different types of silkworms.
• It can be differentiated on the basis of lustre and texture. Few examples are Kosa, tassar, mooga, etc. They are produced by various types of silk moths. One of the common types is the mulberry silk moth.

Development of Silk Moth

Sericulture

• Rearing silkworms to produce raw silk is called sericulture.
• In this process, silkworms are reared at appropriate temperature and humidity to get silk threads from cocoons.

Processing Silk Obtained from Cocoons

• Cocoons are collected and left under the sun, or boiled for separating out the silk fibres.
• After that reeling of silk is done, the process of unwinding silk from a cocoon.
• Then, the spinning of silk fibres into threads is done.
• The silk threads obtained are woven into desired clothes.

Natural Fibres vs. Synthetic Fibres

Natural Fibres

• The naturally occurring fibres that humans derive from plants or animals are known as natural fibres.
• Animal fibres: These are the fibres that are acquired from animals. For example Wool, silk etc.
• Plant fibres: These are the ones that are obtained from plants. These fibres are extracted from the plants to make fabrics.

Synthetic Fibres

• Fibres that are made by humans using chemical substances are known as synthetic or man-made fibres.
• These are more durable than natural fibres.
• For example:- Polyester, Nylon,  Acrylic etc.

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