CG SCERT Chhattisgarh State Board Class 8 Science and Technology Chapter 2 Synthetic Fibres & Plastics Exercises Questions and Answers.
Table 2.1: Natural and Synthetic fibres
|S. No.||Name of article||Type of fibre (Natural / Synthetic)|
(1) What are synthetic fibres?
Ans. A synthetic fibre is also a chain of small units joined together.
(2.) Why should not we wear synthetic fabric while working in the kitchen?
Ans. We have observed that synthetic fibres melt on heating. If the clothes catch fire. it can be a disaster. This fabric melts and shrinks that is because we should not wear synthetic fibre wgile working in the kitchen.
Table 2.2 – Articles made of plastic and their uses.
|Sr. No.||Bane of Plastic Articles||Uses|
|1||Container||Its help us to store foods|
|2||Comb||Its help us to decorating hair.|
|3||Bucket||We can store water by this.|
|4||Plate||We can serve any food by this.|
|Sr. No.||Plastic articles||On forcing||On heating|
|Bends easily/ breaks/ no effect||Deformed / melts / no effect|
(1.) Differentiate between thermoplastic and thermosetting plastics.
|(i) Some plastic articles gets deformed easily on heating and can be bent easily such plastics are known as thermoplastic.||(i) There are some plastic which when moulded once, cannot be softened by heating. The are called the thermosetting plastic.|
|(ii) It can be reshaped and reused.||(ii) It can be reshaped.|
|(iii) It is soften on heating.||(iii) It does not soften on heating.|
(2.) Why electrical switches are made from thermosetting plastics?
Ans. Thermosetting plastics are poor conductor of heat and electricity. It resists fire and can tolerate heat better than other plastics. That is because electrical switches are made from thermosetting plastics.
(3.) Plastics are a cause of environmental pollution. Explain by giving two examples.
Ans. We make extensive use of plastic goods, polythene bags etc. in our daily life. That is because plastic waste keeps getting accumulated in our homes. Ultimately plastic finds its way to the garbage bins, drains, beside the roads or in open grounds. So disposal of plastic has became a major problem.
(1) (i) Synthetics fibres are – (d) All of the above.
(ii) The type of plastic used in making combs is – (a) Thermosetting plastic.
(iii) Clothes of firemen are made from – (b) Melamine.
(iv) Artificial silk is – (c) Rayonn.
(v) PET is- (b) Polyester.
(2) (1) Rayon – made from wood pulp.
(2) Nylon – Used in making parachutes and ropes.
(3) Thermoplastic – Can be moulded easily by heating.
(4) Polyester – fabrics do not wrinkle easily.
(5) Thermosetting platic – Can’t be moulded upon heating.
(3.) Name any three objects made from nylon that shows its strength.
Ans. The three objects made from nylon, these are – ropes, parachutes, fishing net.
(4.) Why PET containers are preferred to store food items?
Ans. PET is a very familiar form of polyester. It does not get wrinkles easily. That is because PET containers are preferred to store food items.