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Q1. We should not wear fabrics made from synthetic fibres in hot summer weather. Why?

Solution

We should not wear fabrics made from synthetic fibres in hot summer weather because most of the synthetic fibres absorb very little moisture. Thus, they become sticky when body sweats which makes them uncomfortable to wear in hot weather.

Q2. Place a plastic spoon and a metal spoon in a jug of hot water. Which one can you hold directly? Why?

Solution

We can hold the plastic spoon directly in a jug of hot water. This is because plastics are poor conductor of heat.

Q3. Burning of plastics is not advisable. Give one reason to support this statement.

Solution

Burning of plastics is not advisable as it releases poisonous gases into the atmosphere.

Q4. Plastic pipes are preferred than metal pipes. Why?

Solution

Plastic pipes are preferred than metal pipes as plastics are corrosion free.

Q5. Give four common uses of nylon fibres.

Solution

Nylon fibres are most often used for making stockings, tooth brushes, ropes and parachutes.

Q6. Both nylon and rayon are man-made fibres. Is there any difference between the two? Explain.

Solution

Yes, nylon and rayon differ in the source from which they are obtained. Rayon is obtained by the chemical treatment of wood pulp which is a natural source while nylon is made without using any natural raw material. It is obtained from coal, water and air.

Q7. Name the following: A. Polyester mixed with cotton B. Polyester mixed with wool

Solution

(A) When polyester is mixed with cotton, it is called Polycot.(B) When polyester is mixed with wool, it is called Polywool.

Q8. Mention two properties of polyester which makes it suitable for making shirts.

Solution

a. Fabric made from polyester fibre does not get wrinkled easily.b. It is easy to wash and gets dried easily.

Q9. Give reason. Thermoplastics can be recycled.

Solution

Thermoplastics are made up of linear chains of molecules with a few cross linkages. This allows them to soften when heated and to be bent into a variety of shapes and forms.

Q10. Most of the fabrics made from synthetic fibres should be ironed very carefully. Why?

Solution

The fabrics made from synthetic fibres should be ironed very carefully because they melt very easily on heating.

Q11. Name the polyester used for making bottles, films and other useful products.

Solution

PET is a very popular form of polyester used for making bottles, films and other useful products.

Q12. You must have seen PET jars and bottles used by your mother in kitchen for storing rice, sugar etc. What are these PET jars and bottles made of?

Solution

PET jars and bottles used in kitchen are made of polyester.

Q13. Why are plastic handles preferred in sauce pan?

Solution

Plastic handles are preferred in sauce pan because they are bad conductor of heat. Thus, they do not get heated and burn hands.

Q14. Why is it advised not to wear fabrics made of synthetic fibres while working in kitchen or near any other source of fire?

Solution

We should not wear fabrics made of synthetic fibres while working in kitchen or near any other source of fire because they catch fire easily.

Q15. What can happen if a person wearing polyester clothes catches fire?

Solution

Polyester on burning melts and sticks to the body of the person wearing it.

Q16. List the characteristics of synthetic fibres.

Solution

Characteristics of Synthetic Fibres

• Synthetic fibres are very strong and more durable.
• They absorb very little water and dry up quickly.
• They are wrinkle resistant and quite lightweight.
• They are less expensive and readily available.
• The clothes made from synthetic fibres are easier to maintain.

Q17. Suggest some measures to save the environment from plastics.    

Solution

• The biodegradable and non-biodegradable wastes should be collected and disposed separately.
• Most of the thermoplastic wastes can be recycled.
• As a responsible citizen, remember the 4R principle. Reduce, Reuse, Recycle and Recover.

                           

Q18. Plastics are replacing metals in car industry. Give two possible reasons to support your answer.

Solution

Plastics are replacing metals in car industry because:1. Plastics are cheaper than metals. 2. Plastics can be easily moulded in various shapes.

Q19. A thermosetting plastic is used to make kitchenware and fabrics which are fire resistant. Name the thermosetting plastic.

Solution

Melamine is a thermosetting plastic which is used to make kitchenware and fabrics which are fire resistant.

Q20. A cotton shirt and a polyester shirt is dried in the sun. Which one will dry faster and why?

Solution

Polyester shirt will dry faster. Polyester is not a good absorbent of water. Therefore polyester clothes dry faster.

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