NCERT Exemplar Solutions Class 8 Science Coal and Petroleum

Multiple Choice Questions...............

Question 1:  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

(d) plastic 

Solution 1:  (d) plastic

Plastic is a man-made substance, while minerals, water, and soil are natural resources.

Question 2:  Air is a natural resource and cannot be exhausted by human activities. It is known as an inexhaustible natural resource. Which of the following is another inexhaustible natural resource?

(a) coal

(b) petroleum

(c) sun-light

(d) minerals 

Solution 2:  (c) sun-light 

Coal, petroleum, and minerals are non-renewable energy sources that can be depleted, while sunlight is a renewable resource that can be replenished.

Question 3: Which of the following is a pair of exhaustible natural resources?

(a) coal and soil

(b) air and sun-light

(c) water and petroleum

(d) wildlife and minerals 

Solution 3: (d) wildlife and minerals

In all the above options (d) is correct. Wildlife and minerals is a pair of exhaustible natural resources.

Question 4: 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 

Solution 4:  (d) CNG

Compressed natural gas, or CNG, is generated by compressing natural gas. Coke, coal tar, and coal gas are all coal-derived products, while CNG is a petroleum product.

Question 5:  Exhaustible natural resources are:

(a) unlimited in quantity.

(b) not dependent on nature.

(c) limited in quantity.

(d) not exhausted by human activities. 

Solution 5:  (c) limited in quantity.

Natural resources that are exhaustible are finite resources that are available in limited amounts and will be depleted as a result of continued human use. Exhaustible natural resources include wildlife, petroleum, water, and minerals.

Question 6:  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. 

Solution 6:  (d) dead remains of living organisms

Fossil fuels are made up of the bones of living creatures that died millions of years ago. Submerge yourself in the ground.

Question 7:  Coal is formed from the remains of

(a) vegetation only

(b) animals only

(c) both vegetation and animals

(d) neither vegetation nor animals 

Solution 7:  (a) vegetation only

Coal is a fossil fuel that is made up of the fossils of extinct plants and animals. Coal is formed over millions of years through a process known as carbonation.

Question 8:  Which substance is formed by the carbonisation of dead vegetation?

(a) coal

(b) coke

(c) coal gas

(d) coal tar 

Solution 8:  (a) coal 

Coal is formed over millions of years through a process known as carbonation. Dead vegetation is converted into carbon-rich coal in this process, which takes place at extremely high temperatures and pressures. 

Question 9:  Naphthalene balls are obtained from coal tar and are used as:

(a) mosquito repellant

(b) honey bee repellant

(c) moth repellant

(d) snake repellant 

Solution 9:  (c) moth repellant 

Naphthalene balls are a chemical pesticide and deodorant whose distinctive odour drives insects and moths away from naphthalene stored under clothes and other objects.

Question 10: Which of the following is not a constituent of petroleum?

(a) paraffin wax

(b) lubricating oil

(c) petrol

(d) coke 

Solution 10:  (d) Coke

Coke is a pure form of carbon. It is not a constituent of petroleum.

Question 11: Petroleum was formed from organisms:

(a) living on the land

(b) living on the plants

(c) living in the sea

(d) living on the rocks 

Solution 11:  (c) living in the sea 

Petroleum is made up of species that live in the sea. When these creatures died, their bodies sank to the seafloor and were coated in layers of sand and clay. The lack of oxygen, high temperature, and high pressure turned the dead species into petroleum and natural gas over millions of years.

Question 12: Choose the incorrect statement from the following:

(a) It is difficult to transport natural gas through pipes.

(b) The disadvantage of natural gas is that it can not be used directly for burning in homes.

(c) Natural gas is stored under high pressure as compressed natural gas.

(d) Natural gas cannot be used for power generation. 

Solution 12:  (a) It is difficult to transport natural gas through pipes.

Natural gas is a naturally occurring hydrocarbon gas that is produced from deep under the earth's surface from petroleum deposits. Since it is a highly flammable gas, transporting it through pipes is difficult. 

Very Short Answer Questions.........................

Question 13:  You are provided with a mixture of petroleum and water. Can you suggest a method to separate the two? 

Solution 13:   Water is way heavier than petroleum. Decantation is a technique for separating a petroleum and water mixture.

Question 14:  What does CNG stand for and why is it considered to be a better fuel than petrol? 

Solution 14:   Full form of CNG is Compressed Natural Gas.

CNG is considered to be a better fuel than petrol because of the following reasons:

1. No air pollution is created on combustion of CNG.
2. No smoke is created on burning of CNG.
3. CNG does not produce any poisonous gas so it is less harmful to environment.
4. CNG is way more economical than petrol.

Question 15:  Name the petroleum product used as fuel for stoves, lamps and jet aircraft. 

Solution 15:   Kerosene is a petroleum product that can be used to power stoves, lamps, and jet planes.

Question 16:  Fill in the blanks in the following sentences.

(a) Coal is one of the ________ used to cook food.

(b) When heated in air, coal burns and produces mainly ________ gas.

(c) Coal tar is a black, thick ________ with an ________ smell.

(d) Petroleum, ________ and ________ are fossil fuels.

(e) Forests and coal are ________ natural resources. 

Solution 16:

(a) Coal is one of the fuels used to cook food.

(b) When heated in air, coal burns and produces mainly Carbon-di-oxide gas.

(c) Coal tar is a black, thick liquid with an unpleasant smell.

(d) Petroleum, Coal and natural gas are fossil fuels.

(e) Forests and coal are exhaustible natural resources.

Question 17:  The underlined words in the following sentences have been jumbled up. Write them in their correct form.

(a) Loca is obtained from mines.

(b) Umpetlore is a fossil fuel.

(c) Rineryfe is a place where various fractions of petroleum are separated.

(d) Keenrose is a fuel used in jet crafts.

(e) Nutsgilh is an example of inexhaustible natural resources. 

Solution 17:

(a) Coal is obtained from mines.

(b) Petroleum is a fossil fuel.

(c) Refinery is a place where various fractions of petroleum are separated.

(d) Kerosene is a fuel used in jet crafts.

(e) Sunlight is an example of inexhaustible natural resources.

Question 18:  Fill in the blanks.

(a) The slow process of conversion of dead vegetation into coal is called__________.

(b) Coal and petroleum are formed from the dead remains of organisms and are known as __________.

(c) The black thick liquid with __________ smell is known as coal tar.

(d) During the processing of coal to get coke, coal tar and __________ are also obtained.

(e) The process of separating the various constituents of petroleum is known as __________.

(f) Excessive burning of fossil fuels is a major cause of __________. 

Solution 18:

(a) The slow process of conversion of dead vegetation into coal is called carbonisation.

(b) Coal and petroleum are formed from the dead remains of organisms and are known as fossil fuels.

(c) The black thick liquid with an unpleasant smell is known as coal tar.

(d) During the processing of coal to get a coke, coal tar and coal gas are also obtained.

(e) The process of separating the various constituents of petroleum is known as refining.

(f) Excessive burning of fossil fuels is a major cause of air pollution.

Question 19:  Write True/False against the following statements.

(a) Oxygen is an exhaustible natural resource.

(b) Resources which are present in unlimited quantity in nature are called exhaustible natural resources.

(c) Wildlife is an exhaustible natural resource.

(d) Under high temperature and pressure, dead plants get slowly converted to coal.

(e) CNG is less polluting fuel than petrol and diesel. 

Solution 19:

a) False- Oxygen is inexhaustible natural resource.

b) False- Inexhaustible natural resources are those that are abundant in nature and cannot be depleted.

(c) True

(d) True

(e) True

Short Answer Questions.........................

Question 20: Sunlight and air are inexhaustible natural resources. Comment. 

Solution 20:  In nature, sunlight and air are abundant, and they are unlikely to be depleted by human activity or any other means. As a result, sunlight and air are limitless natural resources.

Question 21:  Some natural resources are given in a box. Classify them into the exhaustible and inexhaustible natural resources.

Air, Coal, Natural gas, Sunlight, Petroleum, Minerals, Forests and Oxygen. 

Solution 21:

Question 22:  Write two important uses of coke. 

Solution 22:    Two important uses of coke are given below:

• Coke is used in the steel-making process.
• Coke is used in extraction of many metals.

Question 23:  Write the characteristics and some important uses of coal. 

Solution 23:   The characteristics of coal are:

• Coal is black in colour.
• It is Flammable.
• It emits CO₂ as it is burned in the air.
• Coal is a hard fossil fuel.    

The uses of coal are:

• Coal is used to produce electricity in various thermal power plants.
• Coal is a kind of fuel that is used to cook the food.
• Coal is used as a fuel in a variety of industries.
• It was previously used in railway engines to generate steam to power them.

Question 24:   Look at the figure given below, where petroleum and natural gas deposits are shown. Why do we find the oil layer above the water layer?

Solution 24:   Since oil is lighter than water, it floats above the water layer and is contained above the water layer.

Question 25:  Fill in the blanks and complete the story.

About 300 million years ago the earth had dense ________ in low lying wetland areas. Due to natural processes, like ______, these forests got buried under the ________. As more ________ deposited over them, they were compressed. The ________ also rose as they sank deeper and deeper. Under high ________ and high ________, dead plants got slowly converted into coal. 

Solution 25:   About 300 million years ago the earth had dense forests in low lying wetland areas. Due to natural processes, like floods, these forests got buried under the soil. As more soil deposited over them, they were compressed. The temperature also rose as they sank deeper and deeper. Under high pressure and high temperature, dead plants got slowly converted into coal.

Question 26:  Match the items given in Column I with the items of Column II.

Solution 26:

 Long Answer Questions.......................

Question 27:  Name the products obtained and their uses when coal is processed in industry. 

Solution 27:  Coke, coal tar, and coal gas are the by-products of the coal-burning process in industry.

Uses of these products are:

1. Coal tar is used as a starting material for a variety of products, including synthetic dyes, medicines, explosives, perfumes, and paints.
2. In the extraction of metals, coke is used as a reducing agent.
3. Coal gas is used as a source of energy.

Question 28:  We say fossil fuels will last only for a few hundred years. Comment.  

Solution 28:  It takes millions of years for fossil fuels to be turned into these fuels. Fossil fuel formation necessitates special conditions, which aren't always present. As a result, their dwindling supply would only last a few hundred years.

Question 29:  We read in newspapers that burning of fuels is a major cause of global warming. Explain why? 

Solution 29:   Carbon dioxide, carbon monoxide, and SO₂ gases are released as fuels are burned. They are greenhouse gases, which not only lead to air pollution but also to global warming by absorbing solar radiation.

Question 30:  While driving what are the tips we must follow to save petrol/ diesel/natural gas? 

Solution 30:    The tips we must follow to save petrol/ diesel/natural gases are as follow: 

• Make sure the tyre pressure is right.
• Maintenance of vehicle is very necessary, ensure it on regular basis.
• As far as possible, maintain a steady and moderate velocity.
• At traffic lights or other places where you must wait, switch off the engine.

Question 31:  Imagine that all the exhaustible natural resources are exhausted by human activities. Do you think the survival of living beings would be possible? If yes, why? If not, why not? 

Solution 31:   If all of the finite natural resources are depleted as a result of human actions, living beings would be unable to survive. Today, fossil fuels are a critical source of energy for us. It produces heat and light as fossil fuels are burned. The heat produced can be used to cook food or power engines like automobiles. It is also used to produce electricity in power plants, where coal is the most common fuel.

Question 32:  Why petrol is an exhaustible natural resource, whereas sunlight is not? Explain. 

Solution 32:   Petrol is a fossil fuel that is produced by the decomposition of buried and plants deep beneath the earth's surface over many years. Millions of years are needed to produce petrol. If we use more gasoline than is needed, it will run out. The light, on the other hand, is a never-ending and limitless source of energy. The sun is an endless source of energy that will never run out.

Question 33:  Write some important uses of the various constituents of petroleum. 

Solution 33:   Important uses of constituents of petroleum are:

Question 34:  Coal reserves are said to be enough to last for another hundred years. Do you think we need to worry in such a case? Why or why not? 

Solution 34:   There are enough coal reserves to last another hundred years, according to reports. And once the current coal resources have been depleted, there will be no more coal available. It will take millions of years to manufacture coal. In the absence of oxygen, dead organisms can be buried in the soil and decompose. Many of these processes take millions of years to complete.

Question 35:  What steps would you suggest for the judicious use of fossil fuels? 

Solution 35:   Steps to take to ensure that fossil fuels are used wisely: 

• Just use fossil fuels when absolutely necessary.
• Use Alternate sources of energy like, solar, wind and biomass should be used in place of fossil fuels.
• Natural gas can be used instead of fossil fuels.
• Switch off automobile engine while standing in traffic.
• Wherever feasible, use solar energy.

Question 36:  Complete the crossword given below with the help of the clues:

Across

1. Fuels obtained form dead remains of living organisms. (6,5)

2. A process by which the various constituents of petroleum are separated. (8)

3. A porous black substance obtained form of coal. (4)

4. Another name for motor fuel. (6)

Down

5. The substance obtained by carbonisation. (4)

6. Fuel for heavy motor vehicles. (6)

7. A petroleum product used for road surfacing. (7)

8. Dead remains of sea animals got converted into it. (9) 

Solution 36: