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ScienceClass 8CBSE

Petroleum was formed from organisms: (a) living on the land (b) living on the plants (c) living in the sea living on the rocks

Soln: Answer is (c) living in the sea Explanation: Petroleum was formed from organisms living in the sea. As these organisms died, their bodies settled at the bottom of the sea and got covered with layers of sand and clay. Over millions of years, absence of air, high temperature and high pressure transformed the dead organisms into petroleum and natural gas.

ScienceClass 8CBSE

Which of the following is not a constituent of petroleum? (a) paraffin wax (b) lubricating oil (c) petrol coke

Soln: Answer is (b) lubricating oil Explanation: Lubricating oil is obtained from crude petroleum.

ScienceClass 8CBSE

Naphthalene balls are obtained from coal tar and are used as (a) mosquito repellant (b) honey bee repellant (c) moth repellant snake repellant

Answer is (c) moth repellant Explanation: Characteristic smell of naphthalene makes the insects and moth run away from naphthalene stored under clothes etc.

ScienceClass 8CBSE

Coal is formed from the remains of (a) vegetation only (b) animals only (c) both vegetation and animals neither vegetation nor animals

Answer is (d) neither vegetation nor animals Explanation: Coal is formed 300 million years ago when buried plants and trees get decomposed.

ScienceClass 8CBSE

Which substance is formed by the carbonisation of dead vegetation?. (a) coal (b) coke (c) coal gas coal tar

Ansswer is (a) coal Explanation: Coal is formed 300 million years ago when buried plants and trees get decomposed.

ScienceClass 8CBSE

1. Fossil fuels are obtained from: (a) remains of non-living materials. (b) dead remains of birds only. (c) dead remains of insects only. (d) dead remains of living organisms.

Answer is (a) remains of non-living materials. Explanation: Fossil fuels are obtained millions of years ago remains of non-living materials. Get buried under the earth.

ScienceClass 8CBSE

Exhaustible natural resources are: (a) unlimited in quantity. (b) not dependent on nature. (c) limited in quantity. (d) not exhausted by human activities.

Answer is (c) limited in quantity. Explanation: Exhaustible natural resources are limited and they get exhausted by human activities.

ScienceClass 8CBSE

1. Coal is processed in industries to get some useful products. Which of the following is not obtained from coal? (a) coke (b) coal tar (c) coal gas (d) CNG

Soln: Answer is (d) CNG Explanation: CNG is compressed natural gas which is made by compressing the natural gas. CNG is a petroleum product whereas other options provided are obtained from coal.

ScienceClass 8CBSE

Which of the following is a pair of exhaustible natural resources. (a) coal and soil (b) air and sun-light (c) water and petroleum wild life and minerals

Soln: Answer is (d) wild life and minerals Explanation: In option a there is soil, In option b there is sunlight and in option c there is water which will not get exhausted hence option d) is right.

ScienceClass 8CBSE

Air is a natural resource and cannot be exhausted by human activities. It is known as inexhaustible natural resource. Which of the following is another inexhaustible natural resource? (a) coal (b) petroleum (c) sun-light minerals

Soln: Answer is (c) sun-light Explanation: Petroleum and minerals are non-renewable sources of energy which can get exhausted whereas sunlight is a renewable resource.

ScienceClass 8CBSE

Various materials which are obtained from nature are called natural resources. Which of the following is not a natural resource? (a) minerals (b) water (c) soil plastic

Answer is (d) plastic Explanation: Minerals, water and soil are natural resources whereas plastic is a man made substance.

ScienceClass 8CBSE

Despite being very useful it is advised to restrict the use of plastic. Why is it so? Can you suggest some methods to limit its consumption?

Plastic is a non-biodegradable material which poses serious threat to the nature. Disposing of plastic waste is the biggest problem we face to regret the use of plastics. Plastics cause soil pollution and air pollution on burning. Usage of plastic should be reduced and used plastic should be recycled and reused to reduce its consumption.

ScienceClass 8CBSE

Write the importance of synthetic polymers in our life.

Following are the points to justify the importance of synthetic polymers in our life. Nylon It is used for making ropes for rock climbing, fishing nets, raincoats, parachutes and tyre cords, Acrylic It is used for sweaters, tracksuits, linings for boots and gloves and In furnishing fabrics and Terylene It is used in the textile industry to make clothes like sarees, tapestry and dress It is also mixed with a natural fibre like cotton and wool to make more variety of clothes. Plastics It is used to store food item, water, milk, pickles, dry food, etc. Plastic containers seem most convenient. This is because of lightweight, low price, good strength and easy handling as compared to Plastics are used in cars, air crafts and spacecraft.

ScienceClass 8CBSE

Indicate whether the following statements are True or False. Also write the false statements in their correct form. (i) The fabric terywool is obtained by mixing terylene and wool. (ii) Synthetic fibres do not melt on heating. (iii) It is risky to wear synthetic clothes while working in the kitchen. (iv) Most of the plastics are biodegradable.

True False- Synthetic fibres do not melt on True because synthetic clotes melts on exposure to heat False- Plastics are non-biodegradable

ScienceClass 8CBSE

1. Unscramble the jumbled words given below, related to synthetic materials. (a) anory (b) lopmery (c) relyteen (d) laspict (e) yespolter felton

Soln: rayon polymer terylene plastic polyester Teflon

ScienceClass 8CBSE

Match items in List A with the items of list B. List A List B (a) nylon (i) non-stick coating (b) PET (ii) electric switches (c) rayon (iii) parachutes (d) thermosetting plastics (iv) polyester teflon (v) artificial silk

List A List B nylon (iii) parachutes PET (iv) polyester rayon (v) artificial silk thermosetting plastics (ii) electric switches teflon (i) non-stick coating

ScienceClass 8CBSE

Fill in the blanks. (i) A polymer is a chain of many small units joined together which are called . (ii) The synthetic fibres are also known as fibres. (iii) The first fully synthetic fibre was . (iv) A fibre similar to wool is . A plastic used for making crockery is

A polymer is a chain of many small units joined together which are called The synthetic fibres are also known as man made The first fully synthetic fibre was Nylon. A fibre similar to wool is A plastic used for making crockery is melamine

ScienceClass 8CBSE

PVC (polyvinyl chloride) is a thermoplastic and is used for making toys, chappals, etc. Bakelite is a thermosetting plastic and is used for making electrical switches, handles of various utensils, etc. Can you write the major difference between these two types of plastics?

On heating Thermo plastics get deformed and they can be easily bent . Whereas Thermosetting plastics cannot be softened by heating.

ScienceClass 8CBSE

A lady went to the market to buy a blanket. The shopkeeper showed her blankets made of acrylic fibres as well as made of wool. She preferred to buy an acrylic blanket. Can you guess why?

Lady prefer acrylic blanket over wool blankets because acrylic blankets are cheap, light in weight, more durable and are available in variety of colours and designs. They can be easily washed at home

ScienceClass 8CBSE

Rohit took with him some nylon ropes, when he was going for rock climbing. Can you tell why he selected nylon ropes instead of ropes made of cotton or jute?

Because Nylon ropes are strong, flexible and elastic when compared to jute and cotton ropes. Acrylic blankets are cheap, light in weight, more durable and are available in variety of colours and designs. They can be easily washed at home.

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