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Q1. (a) What are petrochemicals? (b) Which conditions under the sea formed petroleum? (c) Why natural gas is considered as one of the most important forms of fossil fuel?

Solution

(a) Various useful constituents obtained from petroleum are called petrochemicals i.e. petroleum gas, petrol, diesel, paraffin wax, lubricating oil etc. (b) Absence of air, high temperature and high pressure are the conditions responsible for formation of petroleum under the sea. (c) Natural gas considered one of the most important forms of fossil fuel because it is very easy to transport through pipes and cylinders.

Q2. Justify the statement: Coal is formed by carbonisation.

Solution

Carbonisation is the conversion of organic matter to carbon containing product. Coal mainly contains carbon. Therefore, the conversion of dead vegetation into coal is called carbonisation.

Q3. Why is it necessary to use coal economically?

Solution

There are two main reasons for which economical use of coal is necessary. They are as follows: 1. Coal is exhaustible source. If it is used indiscriminately, it will be exhausted, as it is present in nature in limited amount. It takes millions of years to form fossil fuels, so it is not possible to make new fossil fuels artificially. 2. Secondly, coal generates polluting gases on burning. Coal is almost carbon and produces carbondioxide on burning, which pollutes our environment. These polluting emissions have given rise to dangers of global warming and air pollution. So, their limited and economic use can control pollution and give better environment to live in.

Q4. Why can't we prepare coal in our laboratories?

Solution

Coal cannot be prepared in our laboratories because it took millions of years to convert dead bodies of plants to get converted in coal. Moreover, such conditions necessary for the conversion of dead bodies into fossil fuel cannot be created in laboratories.

Q5. Why is it not possible to produce petroleum in man-made environment?

Solution

Petroleum cannot be produced in man-made environment as its formation is a very slow process. Also, the condition of high temperature and pressure is very difficult to maintain.

Q6. Coal is a fossil fuel. Give reasons.

Solution

Coal is classified as fossil fuel because it is formed from buried dead remains of living organisms that were subjected to high pressure and temperature.

Q7. Why is it necessary to use petroleum economically?

Solution

There are two main reasons for which economical use of petroleum is necessary. They are as follows: 1. Petroleum is exhaustible source. If it is used indiscriminately, it will be exhausted, as it is present in nature in limited amount. It takes millions of years to form fossil fuels, so it is not possible to make new fossil fuels artificially. 2. Secondly, constituents of petroleum especially petrol and diesel generate polluting gases on burning. These polluting emissions have given rise to dangers of global warming and air pollution. So, their limited and economic use can control pollution and give better environment to live in.

Q8. A substance is a black, hard and porous which is almost the purest form of carbon and is obtained by destructive distillation of coal. Identify the substance and write its uses.

Solution

Coke is a black, hard and porous substance which is almost the purest form of carbon and is obtained by destructive distillation of coal. (i) It is used to manufacture steel. (ii) It is used in extraction of many metals.

Q9. (a) What is destructive distillation of coal? (b) What are the various products of coal obtained by destructive distillation of coal? Explain them along with their uses.

Solution

(a) The strong heating of coal in the absence of air is called destructive distillation of coal. (b) The various products obtained by destructive distillation of coal are: coal gas, coal tar and coke. 1. Coal Gas:  Coal gas is a gaseous fuel which is obtained by the strong heating of coal in the absence of air during the processing of coal to get coke. Coal gas is mainly a mixture of methane and hydrogen, with some carbon monoxide. All the gases present in coal gas can burn to produce heat, due to which coal gas is an excellent fuel (having high calorific value). Coal gas is used as a fuel in industries. These days, however, coal gas is used as a source of heat rather than light.  2. Coal Tar: Coal tar is a thick, black liquid having an unpleasant smell which is obtained by heating coal in the absence of air. Coal tar is not a single compound. Coal tar is a mixture of about 200 carbon compounds (or organic compounds). The products of coal tar are used to make synthetic fibres, drugs (medicines), plastics, synthetic dyes, perfumes, paints, varnishes, pesticides, photographic materials, roofing materials and explosives, etc. Coal tar has been traditionally used for metalling the roads. 3. Coke: Coke is a tough and porous black solid substance Coke is prepared by heating coal in the absence of air. Coke is an almost pure form of carbon. Coke is mainly used as a reducing agent in the extraction of metals (like iron, zinc etc.) Coke is used in the manufacture of steel. Coke is also used as a fuel.   

Q10. List two advantages of using CNG as fuel.

Solution

Advantages of using CNG: 1. It is a clean fuel and does not cause much pollution. 2. It can be directly supplied to home and industry through pipeline.

Q11. How are fossil fuels formed?

Solution

When plants and animals die, they get buried under the soil. As more soil deposits on them, with increasing temperature and pressure, they get converted to fossil fuels.

Q12. We can use inexhaustible resource in unlimited quantity. Why?

Solution

Inexhaustible resources are available in unlimited quantity in nature and can be reproduced easily.

Q13. Why is crude petroleum sent to a refinery?

Solution

The refinery is a place where petroleum is separated into useful constituents or fractions. All fractions of petroleum like petrol, LPG, diesel, etc have various uses.

Q14. Describe the formation of coal.

Solution

Coal is formed by dead remains of plants. Millions of years ago vegetation in forests got trapped under soil layers due to earthquakes and volcanic eruptions. More soil layers got deposited on it and it went deeper beneath the earth. This raised the temperature and pressure beneath the soil. This initiated the process of burning these dead remains. Slowly all the vegetations got converted into coal which is a rich form of carbon. This whole process is also called carbonization.

Q15. (a) Which product of coal is used in anti-dandruff shampoos.State its any other use. (b) How is it obtained?

Solution

(a) Coal tar is used in anti-dandruff shampoos.It is used in metalling of roads. (b) It is obtained as a by-product of the process of manufacturing coke.

Q16. Can petroleum and natural gas be prepared in laboratory? Give reason for your answer.

Solution

No, petroleum and natural gas cannot be prepared in our laboratories because it took millions of years to convert dead bodies of plants and animals to get converted in petroleum. Moreover, such conditions necessary for conversion of dead bodies into fossil fuel cannot be created in laboratories.

Q17. Why is petroleum sometimes called 'black gold'?

Solution

Petroleum is sometimes called 'black gold' because of its great commercial importance and uses.

Q18. A gas is obtained during destructive distillation of coal. Identify the gas. How is it useful?

Solution

A gas obtained during destructive distillation of coal is coal gas. (i) It is used as fuel in coal processing plants and in various industrial units situated near coal processing plants. (ii) Coal gas was used by Americans and Britishers for street lightening.

Q19. What precautionary measures we can take to conserve petrol or diesel?

Solution

Some important tips can help in conserving fuel: 1. We should immediately switch off the vehicle when not moving even temporarily. 2. Drive at an average and constant speed. Speed variation consumes more fuel. 3. Maintain the vehicle properly and getting it serviced at regular intervals. 4. Vehicle pooling is very important.

Q20. Where is petroleum found and how is it extracted?

Solution

Petroleum is found in sea or under earth. They are found under overlying impervious rocks. It is lighter than water, so does not get mixed with it and moves upward near the capping rocks. Wells are dug into these rocks to pull off the petroleum.

Q21. To which process coal is put to get some useful products? Explain the process and name the products obtained from the process.

Solution

Destructive distillation. Burning of coal in absence of air or oxygen to obtain some useful constituents is called destructive distillation. Following constituents are obtained from this process: (a)Coke(b) Coal tar(c) Coal gas

Q22. Why is it important to conserve coal?

Solution

Conservation of coal is necessary as it is an exhaustible natural resource.

Q23. (a) What is CNG? (b) How is CNG related to natural gas? (c) What is the advantage of CNG over petrol and diesel?

Solution

(a) CNG is compressed natural gas which is a fossil fuel. (b) When natural gas is stored under very high pressure then it is known as compressed natural gas or CNG as it is kept compressed under high pressure. (c) CNG does not cause pollution on usage as in case of other petrochemicals like petrol and diesel. Therefore, it can be directly burnt in homes and factories for cooking and other purposes. It is also used as pollution free fuel for vehicles and in power generation.

Q24. Why is coal used as fuel?

Solution

Coal is used as a fuel as it produces a lot of light and heat energy on burning.

Q25. Give two uses of coal tar.

Solution

Coal tar is used in: It is used as a starting material for manufacturing synthetic dyes. It is used as a starting material for manufacturing drugs

Q26. (a) Which petroleum product is used for metalling the roads in place of coal-tar? Give its one use. (b) Which petroleum product is used in ointments and in candles? Give its one use. (c) Which petroleum product is used as domestic fuel? Give its one use.

Solution

(a) Bitumen is used for metalling the roads in place of coal-tar. It is also used in paints. (b) Paraffin wax is used in ointments and in candles. It is also used in Vaselines. (c) Liquefied petroleum gas (L.P.G) is used as domestic fuel. It is also used as fuel in vehicles and industry.

Q27. Do you think coal will be available in many years to come? Why?

Solution

No, coal will not be available for many years to come. This is because coal is being consumed at a faster rate than it is produced.

Q28. What is petroleum? How was it formed? How are the different constituents of petroleum separated?

Solution

Petroleum is a fossil fuel which got formed by the dead remains of the sea animals. These animals slowly got trapped under soil and clay and more deposits were formed with time. Due to depth, the temperature and pressure raised and over the years they got converted into petroleum oil. Since oil is lighter than water, it did not get mixed with water and got raised to the superficial rocks, which did not allow it to pass through them. Petroleum is a mixture of various useful substances. Thus, it is refined to separate these useful by-products in petroleum refineries by the process of fractional distillation of petroleum.

Q29. Where is liquefied petroleum gas mostly used?

Solution

Liquefied petroleum gas (LPG) is most commonly used as fuel in homes and industry.

Q30. How many kinds of natural resources are there on the basis of availability of materials? Define them and give examples for each.

Solution

On the basis of availability of materials, natural resources are of two types: Inexhaustible and exhaustible. Inexhaustible natural resources are those which are present in nature in unlimited amounts and can never get finished by human activities. For example, air, sunlight, soil etc. Exhaustible natural resources are those which are present in nature in limited amounts and can get finished by human activities. For example, petroleum, natural gas, coal etc.

Q31. A substance that is black hard stone which is formed by dead remains of the living organisms and is mainly used as fossil fuel. Identify that substance and write its uses.

Solution

Coal is that fossil fuel which is as hard as a stone and is black in colour. Uses: (i) It is used as fuel to cook food. (ii) It is used to run trains, as it is burnt to generate steam in engine.

Q32. (a) Why is solar energy considered the real source of energy of coal? (b) Give uses of coal (any six).

Solution

(a) The real source of energy of coal is the solar enrgy because the plants and trees which decomposed to form coal grew on the earth by absorbing sunlight energy during the process of photosynthesis. (b) Uses of coal: (i) Coal is used as a fuel in homes and industry. (ii) Coal is used as a fuel at Thermal Power Plants for generating electricity. (iii) Coal is used to make coal gas which is an important industrial fuel. (iv) Coal is used to make coke. (v) Earlier, coal was used as a fuel to make 'steam' to run steam engines of trains. (vi) Coal was also used as a source of organic chemicals.

Q33. A substance is black liquid obtained during destructive distillation of coal. It is thick and smells unpleasant. It is a mixture of hundreds of substances. Identify the substance. How it is useful to us?

Solution

Black liquid obtained during destructive distillation of coal is coal-tar. It is thick and smells unpleasant. It is a mixture of hundreds of substances. (i) Substances obtained from coal-tar are used to manufacture synthetic dyes, drugs, explosives, perfumes, plastics, paints, photographic materials etc. (ii) Earlier, it was also used for surfacing of roads.

Q34. Petroleum is an exhaustible or inexhaustible resource. Why?

Solution

Petroleum is an exhaustible resource as it is present in limited quantity. It cannot be replenished in a short period of time.

Q35. How is fossil fuel linked to global warming?

Solution

The burning of fossil fuels produces carbon dioxide gas as the main by-product which causes green house effect. This leads to global warming.

Q36. (a) Which petroleum product is used as fuel in stoves? Give its one use. (b) Which petroleum product is used to lubricate metal parts? Give its one use. (c) Which petroleum product is used as fuel in light vehicles like scooters, cars etc.? Give its one use.

Solution

(a) Kerosene is used as fuel in stoves. It is also used in lamps and jet aircrafts. (b) Lubricating oil is used to lubricate metal parts. It is also used to lubricate machines. (c) Petrol is used as fuel in light vehicles. It is also used as aviation fuel and used for dry cleaning of fabrics.

Q37. List two things that we can do in respect to car maintenance to conserve energy?

Solution

We should: 1. Ensure regular and timely servicing of the vehicle. 2. Ensure proper tyre pressure.

Q38. What is the use of coal in thermal plants?

Solution

Coal is used in thermal plants to generate electricity.

Q39. How is natural gas formed?

Solution

Natural gas was formed from the remains of dead sea organisms buried deep below the Earth's surface by layers of sediment (sand, mud, clay etc.). Over long periods of time, the dead organisms were transformed by heat and pressure into natural gas.

Q40. What is diesel? How is it different from petrol?

Solution

Diesel is one of the constituents obtained by refining or fractional distillation of petroleum. It is mainly used as the fuel for vehicles as petrol is used. But it is different from petrol, as it is used as fuel for heavy vehicles like trucks, lories etc., while petrol is used as fuel in light vehicles like cars, scooters, etc.