NCERT Solutions for CBSE Class 8 Science Chapter 3 – Free PDF Download
Free PDF download of NCERT Solutions Science Class 8 Solutions Chapter 3 – Synthetic Fibres and Plastics solved by Expert Science Teachers on CoolGyan.Org. All Chapter 3 – Synthetic Fibres and Plastics Questions with Solutions for NCERT to help you to revise complete Syllabus and Score More marks.
Science Revision Notes for Class 8
|Chapter Name||Synthetic Fibres and Plastics|
|Subject||Science NCERT Solutions|
1. Explain why some fibres are called synthetic.
Ans: Since man-made fibres are obtained by the synthesis of petrochemicals, so they are called synthetic fibres.
2. Mark ( ✓ ) the correct answers :
Rayon is different from synthetic fibres because
(a) It has a silk like appearance.
(b) It is obtained from wood pulp.
(c) Its fibres can also be woven like those of natural fibres.
Ans: (b) it is obtained from wood pulp.
3. Fill in the blanks with appropriate words :
(a) Synthetic fibres are also called __________ or __________ fibres.
(b) Synthetic fibres are synthesized from raw material called __________ .
(c) Like synthetic fibres, plastic is also a ___________ .
Ans: (a) Synthetic fibres are also called artificial or man-made fibres.
(b) Synthetic fibres are synthesized from raw material called polymer.
(c) Like synthetic fibres, plastic is also a petrochemicals.
4. Give examples which indicate that nylon fibres are very strong.
Ans: They are used to make parachutes and ropes for rock climbing.
5. Explain why plastic containers are favored for storing food.
Ans: The main advantages of using plastic for storing food are –
a. Plastic has light weight.
b. Good strength.
c. Easy to handle.
6. Explain the difference between thermoplastic and thermosetting plastics.
|(i) These are the plastics which become soft on heating; they can be melted repeatedly by heating. |
(ii) These are used for making toys, combs and various types of containers.
(iii) Ex- polythene, PVC, polystyrene, etc.
|(i) These are the plastics which do not become soft on being exposed to moderately high temperatures. |
(ii) Used for making electrical switches and handles of various utensils.
(iii) Ex- Bakelite, melamine etc.
7. Explain why the following are made of thermosetting plastics.
(a) Saucepan handles
(b) Electric plug/ switches /plug boards
Ans: (a) Saucepan Handles: Saucepan handles are made from the thermosetting plastics because these are bad conductors of heat. They do not bend or deform on heating.
(b) Electric plug/Switches/Plug Boards: Electric plug/switches/plug boards are made from thermosetting plastics because thermosetting plastics are bad conductor of heat and electricity also. Hence it is used to make such articles.