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8th Synthetic fiber and plastic

Q. Why do we wear clothes?
Ans: We wear clothes for protection against climate and to look smart. Fabric is the material that is used to make clothing or household articles.
Q. Of what material fabrics are made of?
Ans: Fabrics are made up of smaller threads or hair like structure. single hair like structure  is called a fibre. Short fibres are called  Staple fibre . Long fibers are called   Filament fibre
Q. What is natural fibre?
Ans: Fibers obtained from natural sources like plants and animals is called natural fibre. e.g. cotton, Jute, silk, wool, etc
(i)Vegetable Fibres: fibres which are obtained from different plants are called Vegetable Fibres.  For example Cotton is obtained from seed of the plant, jute is obtained from the stem of a plant and coir is the outer covering of coconut
(ii) Animal Fibres: fibres which are obtained from different animal sources is called a Animal Fibres eg sheep goat, rabbits ,camels and silk worm..
Q. What are man-made fibers?
Ans:  Fibres  that are obtained from chemical substance are called manmade fibres. E.g. rayon, polyester, nylon, acrylic (cashmilon)   etc. The first man-made fibre is known as rayon.
Q. State whether the following are true or false and correct the false statements:
(i) Fibre is the basic unit of all fabrics.      (T)                        
 (ii) Filament are short fibres.(F)
(iii) Jute is the outer covering of coconut.(F)                       
(iv) Silk is prepared from the stem of a plant.(F)
(v) Polyester is a staple fibre. (F)
Q. How you distinguish natural fibre and synthetic fibre?
Ans :  BURNING TEST  helps to identify fibers.
COTTON AND RAYON
Catches fire easily
burn with a bright yellow flame
ash
SILK AND WOOL
Does not catch fire easily
Do not burn with a bright yellow flame
Black crushable bead
NYLON, ACRYLIC
Does not catch fire . melts flame  Shrinks away from No definite smell Hard,
Shrinks away from flame. Burns with
 Q. How yarn is made?
Ans: A yarns is a continuous strand made up of a number of fibers which are twisted together.
The process of making yarns from fibres is called spinning. Here the fibres are not only twisted but also pulled out or drawn.
Spinning can be done by using a takli (spindle), a charkha or a spinning machine
Q. State whether the following are true or false:
(i) Yarn is made of a number of fibres.
(ii) Staple fibres are used to make a yarn.
(iii) Spinning is a process of making fibres.
(iv) Spinning increases the strength of yarns.
(v) Twisting increases the strength of the yarns.
(vi) Smoothness of a yarn depends on the twisting of the fibres.
(vii) Blends are made from different fibres.
Q. Define weaving?
Ans: Weaving is the process of interlacing two sets of yarns at right angles to each other to make a fabric.
Weaving is done on looms. Hand operated looms are called handlooms and power operated ones are called power looms. Knitting is interlooping of one or more set of yarns

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