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ScienceClass 8CBSE

A bucket made of plastic does not rust like a bucket made of iron. Why?

Plastic is a non-reactive material. To form rust it should react with water and oxygen. Hence plastic donot form rust.

ScienceClass 8CBSE

Select the articles from the following list which are biodegradable. (a) paper (b) woolen clothes (c) wood (d) aluminium can (e) plastic bag peels of vegetables

Paper Woolen clothes Wood f) peels of vegetables

ScienceClass 8CBSE

Why is it not advisable to burn plastic and synthetic fabrics?

Burning of plastic releases toxic gases which pollutes air. Hence it not advisable to burn plastic and synthetic fabrics.

ScienceClass 8CBSE

Plastic is used for making a large variety of articles of daily use and these articles are very attractive. But it is advised to avoid the use of plastic as far as possible. Why?

Plastic is not bio-degradable and disposing of plastic waste is a major issue. Hence it is advised to avoid the use of plastic as far as possible.

ScienceClass 8CBSE

Plastic articles are available in all possible shapes and sizes. Can you tell why?

It is very easy to make moulds from plastic hence it is available in all possible shapes and sizes.

ScienceClass 8CBSE

Terrycot is made by mixing two types of fibres. Write the names of the fibres.

Terrycot is prepared by mixing terylene and cotton.

ScienceClass 8CBSE

A synthetic fiber which looks like silk is obtained by chemical treatment of wood pulp. It is, therefore, known as artificial silk. What is its common name?

Rayon is known as artificial silk.

ScienceClass 8CBSE

Cotton is a natural polymer. What is its chemical name?

Chemical name of cotton is cellulose.

ScienceClass 8CBSE

The material which is commonly used for making kitchen containers is (a) PVC (b) Acrylic (c) Teflon (d) PET

Answer is (d) PET Explanation: PET or Polyethylene tetra thalate is light weight and it is used in making kitchen containers.

ScienceClass 8CBSE

1. Which of the following groups contain all synthetic substances? (a) Nylon, Terylene, Wool (b) Cotton, Polycot, Rayon (c) PVC, Polythene, Bakelite Acrylic, Silk, Wool

Soln: Answer is (c) PVC, Polythene, Bakelite Explanation: In option a) and c) there is wool which is extracted from animal source. In option b) there is cotton which is from plant source. Hence the answer is (c) PVC, Polythene, Bakelite.

ScienceClass 8CBSE

Which of the following represents the correct match for items in Column A with those in Column B. Column A Column B I. Nylon (i) Thermoplastic II. PVC (ii) Thermosetting plastic III. Bakelite (iii) Fibre (a) I-(ii), II-(iii), III-(i) (b) I-(iii), II-(i), III-(ii) (c) I-(ii), II-(i), III-(iii) (d) I-(iii), II-(ii), III-(i)

Answer is (c) I-(ii), II-(i), III-(iii)

ScienceClass 8CBSE

The most suitable material for the preparation of handles of cooking utensils is (a) Polythene (b) PVC (c) Nylon Bakelite

Soln: Answer is (d) Bakelite Explanation: Bakelite is a bad conductor of heat and it does not get soft on heating hence Bakelite is used to prepare handles of cooking utensils.

ScienceClass 8CBSE

Which of the following is not a common property of plastics? (a) Non-reactive (b) Light in weight (c) Durable Good conductor of electricity

Soln: Answer is (d) Good conductor of electricity Explanation: Plastic is a bad conductor of electricity.

ScienceClass 8CBSE

The material similar to silk in appearance is (a) Nylon (b) Rayon (c) Polyester Terylene

Soln: Answer is (b) Rayon Explanation: Rayon is obtained by chemical treatment of wood pulp. Rayon is cheaper than silk and can be woven like silk.

ScienceClass 8CBSE

Polycot is obtained by mixing (a) nylon and wool (b) polyester and wool (c) nylon and cotton polyester and cotton

Soln: Answer is (d) polyester and cotton

ScienceClass 8CBSE

Which is a thermosetting plastic? (a) Melamine (b) Polythene (c) PVC Nylon

Soln: Answer is (a) Melamine Explanation: Thermosetting plastics when moulded once can not be softened by heating. Examples are bakelite and melamine.

ScienceClass 8CBSE

Which of the following is a source of rayon? (a) Wool (b) PET (c) Wood pulp Silk

Soln: Answer is (a) Wool Explanation: Rayon is obtained by chemical treatment of wool pulp.

ScienceClass 8CBSE

Pick the synthetic fibre out of the following? (a) Cotton (b) Nylon (c) Jute Wool

Soln: Answer is (b) Nylon Explanation: Cotton and Jute are from plant sources, Wool is of animal source whereas Nylon is a synthetic fibre.

ScienceClass 8CBSE

Why should we save paper?

We should save paper for the flowing reason Trees are cut to manufacture In order to save the trees paper should be saved. Saving paper can help in saving water used to manufacture the Usage of chemical can be reduced which will reduce the water

ScienceClass 8CBSE

How does deforestation lead to frequent floods and droughts?

Deforestation will reduce the water holding capacity of the soil due to lack of trees. This reduces infiltration of water into the ground which increase the chances of flood. Cutting of trees leads to accumulation of Carbon-di- oxide in the atmosphere. CO2 traps heat rays from sun which are reflected by earth. This results in increase of temperature on earth. Increase in temperature disturbs water cycle which causes draughts and floods.

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