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ScienceClass 8ICSE

What is PET? State the uses of PET.

Answer “Polyethylene terephthalate is a condensation polymer of ethylene glycol and terephthalic acid.” The by-product of the reaction to create this compound is water so it is an example of condensation or step- growth polymerization. PET is used in manufacturing of the following products: shopping bags, water bottles, videotapes containers and bags clothes and housing material

ScienceClass 8ICSE

Give the important uses of nylon

Answer Nylon is used in ropes, tents, bags, curtains, parachute ropes, socks and ropes for rock climbing.

ScienceClass 8ICSE

What is polyester? Name a popular polyester.

Polyesters are formed as a result of condensation of dicarboxylic acids and diols. The most popular example of polyester is terylene. When ethylene glycol and terephthalic acid is heated at 420 to 460 K in the presence of zinc acetate-antimony trioxide catalyst, the polyester terylene is manufactured. Polycot is popular polyester used in textile manufacturing units.

ScienceClass 8ICSE

Arrange the following fibres in the order of increasing strength (keeping the fibre of least strength first): Nylon, Cotton, Wool, Polyester, Silk

Answer Fibres in the order of increasing strength are nylon, cotton, polyester, nylon and silk.

ScienceClass 8ICSE

State the characteristics of synthetic fibres.

Answer These fibres are filaments that are crystalline in nature Robust and high elasticity Much cheaper compared to natural fibre Stronger than naturally occurring fibre Very durable Dry up quickly hence used in making dress materials Available readily as compared to natural fibres Can be maintained easily Easy to wash

ScienceClass 8ICSE

What is nylon? State the important properties of nylon.

Answer The first fully synthetic fibre, nylon, is a man-made fibre. Back in 1931, it was made purely from coal, water, and air. It did not use raw materials from animals and plants. Properties of nylon are: Nylon is light, strong – stronger than a strand of steel of comparative thickness Nylon has elastic and lustrous properties Nylon is easy to wash

ScienceClass 8ICSE

What is a polymer? Name the natural polymer from which cotton is made.

Answer Synthetic fibres are fibres that are made by man. It is a chain of units put together to form a Polymer. A polymer comprises of these small units put together to form a larger unit. However, some polymers occur freely in nature. Cotton, for instance, is a natural polymer consists of a polymer called cellulose, which is in turn made up of a group of glucose units.

ScienceClass 8ICSE

Which of the two is a thermosetting plastic: PVC or bakelite?

Bakelite is thermosetting plastic.

ScienceClass 8ICSE

Fill in the following blanks with suitable words: (a) Synthetic fibres are also called or fibres. (b) Synthetic fibres are made from raw materials called (c) Like synthetic fibres, plastic is also a (d) The use of plastics can be reduced by using bags made of or instead of polythene bags.

Answer Synthetic fibres are also called man-made or artificial Synthetic fibres are made from raw materials called Like synthetic fibres, plastic is also a The use of plastics can be reduced by using bags made of paper or jute bags instead of polythene

ScienceClass 8ICSE

Name four different plastics.

Polyethene, PVC, Bakelite and melamine are the four different types of plastics

ScienceClass 8ICSE

Give one use of Teflon.

It is used in nonstick cooking vessels.

ScienceClass 8ICSE

Name the form of polyester which is replacing materials like glass and used for making bottles and jars.

Answer The form of polyester which is replacing materials like glass and used for making bottles and jars is Polyethylene terephthalate (PET).

ScienceClass 8ICSE

State one disadvantage of using synthetic fibres for making clothes.

Answer The synthetic fibres melt at high temperatures or on heating. Hence it is advised not to wear synthetic clothes while cooking or during summer.

ScienceClass 8ICSE

To which kind of synthetic fibres does terylene belong?

Terylene belongs to polyester kind of synthetic fibres.

ScienceClass 8ICSE

Which synthetic fibre feels like wool and used as a substitute for wool?

Acrylic is the synthetic fibre feels like wool and used as a substitute for wool.

ScienceClass 8ICSE

Which synthetic fibre contains the organic group similar-to those which give fruits their sweet smell.

Answer Polyester is the synthetic fibre contains the organic group similar-to those which give fruits their sweet smell

ScienceClass 8ICSE

Name the fibre used for making parachutes and rock climbing ropes.

The fibre used for making parachutes and rock climbing ropes is nylon.

ScienceClass 8ICSE

Name the first fully synthetic fibre.

Nylon is the first fully synthetic fibre.

ScienceClass 8ICSE

Name the fibre obtained by the chemical treatment of wood pulp (or cellulose).

The fibre obtained by the chemical treatment of wood pulp (or cellulose) is rayon.

ScienceClass 8ICSE

Name the man-made fibre which is regarded as artificial silk.

The man-made fibre which is regarded as artificial silk is rayon.

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