Synthetic Fibres and Plastics / CBSC Class 8 NOTES
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1- synthetic fibre- fibre that are made by humans being are called synthetic fibres.
2- thermoplastics- plastic that can be reheated and remodeled are called thermoplastic.
3- thermosetting plastics- plastic that cannot be e remodeled after reheating are called thermosetting plastic.
4- non- bio gradable- substances that cannot be decomposed by microorganism are called non- biodegradable
Question-1- what are synthetic fibres? Give two examples?
Ans- fibres that are made by human beings called synthetic fibres. Example- nylon , rayon
Question-2- give two uses each of rayon, polyester and spandex?
Answer- rayon is used for making suits, jackets, scorves, ties, home furnishing cbed sheets, curtains, table cloths, etc. And bandages.
Question-3- what are the properties and uses of Nylon?
* it is elastic and does not lose strength even after repeated use.
* it is lustrous and easy to wash.
* it is waterproof.
Uses- nylon is used for making socks, stockings, tents, umbrellas, parachutes and tarpaulins. Nylon fibres are used for making toothbrush bristles.
Question 4- plastic are poor conductors of heat. What does this property of plastic makes them suitable for ?
Answer- thermal conductivity – plastic have low thermal conductivity C.I.E., they are poor conductors of heat. This makes them suitable for..
* making handles of cooking uses.
* use in refrigerator.
* making container used in in microwave ovens.
Question-5- what do the following stand for- PP , HDPE , PS and PET? Right to use of each?
1-PET(polythene )- making containers for microwave cooking, bottles of carbonated beverages, water bottles, and other food container.
2-HDPE(high density polythene)- making containers for strong and corrosive household and industrial chemical such as breaches and acids.
3-pp(polypropylene)- making retchup bottles, yoggust containers, medicine bottles and automobile battery casing.
4-PS (polypropylene)- thermocol, of form of PS, is used for making disposable cubs and packing material for fragile items like computers and televisions.
Answer- reducing the uses of plastics and recycling plastic objects are two ways of counting .the harmful associated with plastic disposal. Recycling of plastic objects involves collecting, sorting and processing plastic waste with an aim to to reuse the material in in manufacturing other products.
Question-7- what are the advantages and disadvantages of synthetic fibres?
1-advantages of synthetic fibres.
* most synthetic fibre have good elasticity.
* most fibres made of synthetic fibres do not wrinkle easily.
* most synthetic fibre can handle heavy loads without breaking.
2- disadvantages of synthetic fibres.
* most fibres made from synthetic fibres require ironing as they melt easily.
* most fibres made from synthetic fibres absurd very little moisture. they become sticky when the body sweats, which make them uncomfortable to wear in hot weather.
* Most fabrics made from synthetic fibres catch fire very easily. Therefore, it is dangerous to wear them near a source of fire(e.g., while working in the kitchen)
Question-8- describe the general properties of plastics?
1-thermal conductivity- plastic have low thermal conductivity(i-e, they are conductors of heat)
* making handles of cooking vessels.
* use in in refrigerator(as foam care)
* making containers used in microwave oven.
2- electrical conductivity- plastics are poor conductors of electricity.
3- solubility in water- plastic are insoluble in water.
4- effect of flame- most plastic are inflammable.
5- reactivity- plastic do not corrode or rust.
Questions-9- explain the harmful effects associated with the disposal of plastics?
1-plastic that get buried prevent rainwater form seeping into the ground. This water forms muddy puddles on the surface. this also effect the plants growing in the area as they do not get enough water from the soil.
2- when plastic are burned, the produce tonic gases and smack.
3- plastics dumped in water bodies pose a threat to aquatic as tonic substances present in them can cause reproductive failure in in fish and other aquatic organism.
4- most plastic wastage and up lettering roadside and form Agali dumps that harbour many diseases causes organism.
Question-10- list a few thing that can be done to Limit the harmful effect associated with plastic?
answer- a few things that can be done to limit the harmful effects associated with plastic are as follows.
* do not throw plastic waste at roadside or in water bodies. Look for proper garbage beans to disposal them.
* reuse the plastic bags that you have at home.
* do not accept plastic that then you go out for shopping. In street, ask for paper bags for carry a reusable cloth back with you.
* use separate garbage bin at your home and school for or biodegradable and non biodegradable wastes.
Question-10- what are the main difference between thermoplastic and thermosetting plastic? give One example of each?
* liner and lightly cross linked polymers form class of plastics called thermoplastics.
* thermoplastic can be melted by heating and thereafter modulate into you desired soaps. This is a reversible process.
*PVC and LDPE are example of of thermoplastics.
2- thermosetting plastics