Extra 20 important long questions and answers from the chapter:3 "Coal and Petroleum" for Class 8 Science (CBSE):-
1. What is coal? How is it formed?
Ans: Coal is a fossil fuel that is black in colour and is used as a source of energy.
Formation of Coal:
Millions of years ago, dense forests in low-lying wetland areas got buried under soil.
Due to
high temperature and pressure
, these plant remains slowly converted into coal.
This slow process of conversion is called
carbonization
.
Coal mainly consists of
carbon
along with hydrogen, oxygen,
sulphur
, and nitrogen.
Coal is used in
power plants, industries, and domestic cooking
.
It is a
non-renewable resource
as it takes millions of years to form.
2. What are the different types of coal? Explain.
Ans: Coal is classified into different types based on carbon content and energy output.
Anthracite
– Highest carbon content (about 80-90%), burns with high heat, and is the cleanest coal.
Bituminous
– Most commonly used, contains 60-80% carbon, used in power plants and industries.
Lignite
– Lower carbon content (45-55%), produces more smoke, used in electricity generation.
Peat
– Least carbon content (less than 40%), not efficient as a fuel, found in the early stage of coal formation.
These types differ in
energy efficiency, pollution level, and industrial usage
.
3. What are the different products obtained from coal? Give their uses.
Ans: Coal is processed to obtain various products used in industries and households.
Coke
– A porous, black substance used in
steel manufacturing
and metal extraction.
Coal Tar
– A thick, black liquid used in
making roads, synthetic dyes, drugs, and waterproof paints
.
Coal Gas
– Used as an
industrial fuel
for heating and lighting.
Ammonia Liquor
– Used in the production of
fertilizers
.
Carbon Black
– Used in
printing ink, rubber, and tire manufacturing
.
These products are used in
construction, chemical, and fuel industries
.
4. What is petroleum? How is it formed?
Ans: Petroleum is a liquid fossil fuel that is an important energy source.
Formation of Petroleum:
Formed from
dead marine organisms
buried under layers of sand and silt millions of years ago.
Due to
heat and pressure
, these remains converted into
crude oil
.
This oil is extracted through
oil wells
and refined in
petroleum refineries
.
Petroleum is a
mixture of hydrocarbons
like petrol, diesel, and kerosene.
It is also known as
"black gold"
due to its high economic value.
Used in
transportation, industries, and manufacturing of chemicals and plastics
.
5. What is fractional distillation? Explain the various fractions obtained from petroleum.
Ans: Fractional distillation is a process of separating crude oil into different useful components based on their boiling points.
Fractions obtained from petroleum:
Petroleum Gas (LPG)
– Used as
cooking fuel
.
Petrol
– Used in
cars, motorcycles, and aviation fuel
.
Kerosene
– Used as
jet fuel and cooking fuel
.
Diesel
– Used in
buses, trucks, and power generators
.
Lubricating Oil
– Used in
machines and engines
.
Bitumen
– Used for
paving roads and waterproofing
.
6. What is natural gas? What are its uses?
Ans: Natural gas is a fossil fuel found underground along with petroleum.
Uses of Natural Gas:
Compressed Natural Gas (CNG)
– Used as
a clean fuel in vehicles
.
Liquefied Petroleum Gas (LPG)
– Used as
domestic cooking fuel
.
Power generation
– Used in
gas turbines to generate electricity
.
Industrial use
– Used in the
manufacture of fertilizers, chemicals, and glass
.
Eco-friendly
– Produces
less pollution
compared to coal and petroleum.
Easily transportable
– Supplied through
pipelines
to households and industries.
7. Why is petroleum called "black gold"?
Ans: Petroleum is called "black gold" because:
It has
high economic value
due to its widespread use.
It is used to make
fuel (petrol, diesel, kerosene)
.
Used in
transportation, electricity generation, and industries
.
Used in
chemical and plastic industries
to make paints, wax, and detergents.
It is
scarce and expensive
like gold.
Extracted in the form of
crude oil
, which is black in
colour
.
8. How does the burning of fossil fuels affect the environment?
Ans: The burning of fossil fuels causes several environmental issues:
Air pollution
– Releases harmful gases like CO₂, SO₂, and NO₂.
Global warming
– Increases greenhouse gases, leading to climate change.
Acid rain
–
Sulfur
dioxide and nitrogen oxides mix with rain, damaging crops and buildings.
Smog formation
– Reduces visibility and affects health.
Oil spills
– Contaminate water bodies, harming marine life.
Deforestation
– Land clearing for mining and drilling causes habitat loss.
9. How can we conserve fossil fuels?
Ans: Fossil fuels are limited, so we must use them wisely.
Use public transport
instead of private vehicles.
Switch off electrical appliances
when not in use.
Use alternative energy sources
like solar, wind, and hydro energy.
Improve fuel efficiency
in vehicles and industries.
Reduce, Reuse, and Recycle
plastic products.
Use biofuels
like ethanol and biodiesel as substitutes.
10. What are petrochemicals? Give their uses.
Ans: Petrochemicals are chemicals derived from petroleum and natural gas.
Uses of Petrochemicals:
Plastics
– Used in bottles, containers, and packaging.
Synthetic
fibers
– Used in clothes, ropes, and carpets.
Fertilizers
– Made from petroleum derivatives like ammonia.
Rubber and tires
– Used in automobiles.
Cosmetics and medicines
– Used in perfumes, lotions, and pharmaceutical products.
Detergents
– Used in cleaning agents and shampoos.
11. What are fossil fuels? Why are they considered non-renewable?
Ans: Fossil fuels are natural fuels formed from the remains of plants and animals buried under the Earth's surface for millions of years.
Examples: Coal, Petroleum, and Natural Gas.
Why are they non-renewable?
Takes millions of years
to form.
Limited in nature
and cannot be replaced quickly.
Overuse leads to depletion
of resources.
Cannot be artificially created
on a large scale.
Demand is increasing
, but supply is decreasing.
Burning fossil fuels harms the environment
.
12. What are the disadvantages of using fossil fuels?
Ans: Using fossil fuels has many negative effects:
Causes air pollution
– Releases CO₂, SO₂, and NO₂ gases.
Leads to global warming
– CO₂ traps heat, increasing Earth’s temperature.
Causes acid rain
–
Sulphur
dioxide mixes with rainwater, damaging crops and buildings.
Non-renewable
– Once exhausted, they cannot be replaced.
Oil spills
– Harm marine life and pollute water bodies.
Leads to respiratory diseases
– Causes asthma, lung infections, and breathing issues.
13. How does fractional distillation of petroleum work?
Ans: Fractional distillation is the process of separating petroleum into different useful components based on their boiling points.
Process:
Crude oil is heated
in a distillation column.
Different components
evaporate at different temperatures
.
The
vapors
rise and cool down
at different heights.
Heavier fractions
(bitumen, diesel) condense at the bottom.
Lighter fractions
(petrol, kerosene) condense higher up.
The separated components are used in
fuels, industries, and chemicals
.
14. What are the advantages of using natural gas over other fossil fuels?
Ans: Natural gas is a cleaner and efficient fuel compared to coal and petroleum.
Advantages:
Produces less pollution
– Emits fewer harmful gases.
High calorific value
– Provides more energy per unit.
Easy to transport
– Supplied through pipelines.
No residue or smoke
– Does not produce ash or soot.
Used as a fuel in CNG vehicles
– Reduces vehicular pollution.
Used in industries
– For manufacturing chemicals and fertilizers.
15. What are the differences between renewable and non-renewable resources?
Ans:
|
Feature |
Renewable Resources |
Non-Renewable Resources |
|---|---|---|
|
Definition |
Can be replenished naturally |
Limited and take millions of years to form |
|
Examples |
Sunlight, Wind, Water |
Coal, Petroleum, Natural Gas |
|
Availability |
Unlimited supply |
Limited in nature |
|
Environmental Impact |
Eco-friendly |
Causes pollution |
|
Usage |
Used in solar, wind, and hydroelectric power |
Used as fuel for transport and industries |
|
Sustainability |
Can be used forever |
May get exhausted |
16. What is acid rain? How is it caused by burning fossil fuels?
Ans: Acid rain is rainfall that contains harmful acids like sulfuric acid and nitric acid.
Causes:
Burning fossil fuels
releases
sulphur
dioxide (SO₂) and nitrogen oxides (NO₂).
These gases
mix with water vapor
in the atmosphere.
They form
sulfuric acid (H₂SO₄) and nitric acid (HNO₃)
.
These acids
fall with rain
, damaging the environment.
Affects
crops, water bodies, and historical monuments
.
Example: Acid rain has
damaged the Taj Mahal
in India.
17. Why should we reduce the use of fossil fuels?
Ans: Fossil fuels should be conserved to protect the environment and future generations.
Reasons:
Non-renewable
– Once exhausted, they cannot be replaced.
Causes air pollution
– Releases harmful gases.
Leads to global warming
– Increases Earth’s temperature.
Causes acid rain
– Harms agriculture and buildings.
Creates health problems
– Leads to breathing issues.
Alternative energy sources are available
– Solar, wind, and hydroelectric power can replace fossil fuels.
18. What are the uses of bitumen?
Ans: Bitumen is a thick, black, and sticky substance obtained from petroleum.
Uses:
Road construction
– Used to make asphalt roads.
Roofing material
– Used for waterproofing houses.
Sealing cracks
– Used in pipelines and walls.
Soundproofing
– Used in buildings to reduce noise.
Paint and coatings
– Used in protective paints.
Industrial use
– Used in making adhesives and insulation materials.
19. How does mining coal affect the environment?
Ans: Coal mining has serious environmental impacts.
Effects of Coal Mining:
Deforestation
– Large areas of forests are cleared for mining.
Soil erosion
– Removes topsoil, making land infertile.
Water pollution
– Toxic chemicals from mines enter water bodies.
Air pollution
– Releases coal dust, causing lung diseases.
Loss of habitat
– Destroys homes of wildlife.
Land degradation
– Makes land unsuitable for farming.
20. How can we promote the use of alternative energy sources?
Ans: Alternative energy sources can reduce our dependence on fossil fuels.
Ways to Promote Alternative Energy:
Government policies
– Provide incentives for renewable energy projects.
Solar panels
– Use solar energy for electricity and heating.
Wind energy
– Install wind turbines for power generation.
Hydroelectricity
– Increase the use of water dams for electricity.
Public awareness
– Educate people about renewable energy.
Reduce fossil fuel use
– Use bicycles, public transport, and energy-efficient appliances.
