GSEB Class 8 Science Solutions Chapter 5 Coal and Petroleum

Question 1. What are the advantages of using CNG and LPG as fuels?
Answer: The benefits of using CNG and LPG are clear:

• CNG and LPG are clean burning fuels.
• Their total cost is quite low.
• They can be used directly for combustion.
• They are readily available.
• These fuels do not cause air pollution.

In simple words: CNG and LPG are good fuels because they are clean, cheap, easy to use, and don't pollute the air.

Exam Tip: When listing advantages, try to group similar points (e.g., environmental benefits, economic benefits) to make your answer structured and easy to read.

 

Question 2. Name the petroleum product used for surfacing of roads.
Answer: Bitumen is the petroleum product which helps in surfacing roads these days. It provides a durable and smooth surface for traffic.
In simple words: Bitumen, a product from petroleum, is used to build roads.

Exam Tip: Remember specific applications of petroleum products, as these are common factual recall questions.

 

Question 3. Describe how coal is formed from dead vegetation. What is this process called?
Answer: Around 300 million years ago, Earth had thick forests in low-lying wetland regions. Due to different natural events, such as floods and earthquakes, these forests became buried under the soil. The soil then accumulated layer by layer over them, causing compression. Under conditions of high temperature and pressure, the plant matter slowly transformed into coal. This specific process is termed carbonisation.
In simple words: Coal formed over millions of years when dead plants in ancient forests got buried, compressed, and heated underground, a process called carbonisation.

Exam Tip: When describing geological processes, always mention the key conditions like "millions of years," "high temperature," and "pressure" to show a complete understanding.

 

Question 4. Fill in the blanks.
(a) Fossil fuels are __________ and __________
(b) Process of separation of different constituents from petroleum is called __________
(c) Least polluting fuel for vehicles is __________
Answer: The blanks can be completed as follows:
(a) Fossil fuels are Coal, Petroleum, and Natural gas.
(b) Process of separation of different constituents from petroleum is called Refining.
(c) Least polluting fuel for vehicles is Compressed Natural Gas (CNG).
In simple words: Fossil fuels are coal, oil, and natural gas. Separating oil parts is refining. CNG is the least polluting fuel for cars.

Exam Tip: Pay close attention to keywords for fill-in-the-blanks, especially terms related to processes (like refining) and classifications (like types of fossil fuels).

 

Question 5. Tick True/False against the following statements.
(a) Fossil fuels can be made in the laboratory.
(b) CNG is more polluting fuel than petrol.
(c) Coke is almost the pure form of carbon.
(d) Coal tar is a purest mixture of various substances.
(e) Kerosene is not a fossil fuel.
Answer:
(a) False. Fossil fuels take millions of years to form under specific natural conditions and cannot be created artificially in laboratories.
(b) False. CNG is considered a much cleaner fuel than petrol because it produces fewer harmful emissions, making it less polluting.
(c) True. Coke is a nearly pure form of carbon, produced by heating coal in the absence of air, which removes volatile components.
(d) True. Coal tar is actually a complex mixture of hundreds of different substances, resulting from the processing of coal.
(e) False. Kerosene is obtained from petroleum, which is a fossil fuel. Therefore, kerosene itself is a fossil fuel.
In simple words: Fossil fuels cannot be made in a lab, and CNG is less polluting than petrol. Coke is almost pure carbon, and coal tar is a mixture. Kerosene is a fossil fuel.

Exam Tip: For true/false questions, briefly explain your reasoning to support your answer, especially if there's a chance of ambiguity or partial credit.

 

Question 6. Explain why fossil fuels are exhaustible natural resources.
Answer: Fossil fuels are present in limited amounts within nature. They can be completely used up by human actions. Therefore, fossil fuels are referred to as exhaustible natural resources, meaning their supply is not endless.
In simple words: Fossil fuels are exhaustible because there's only a limited amount on Earth, and human activities can use them all up.

Exam Tip: Define "exhaustible" clearly in your answer and explain why fossil fuels fit this definition due to their formation time and limited quantity.

 

Question 7. Describe characteristics and uses of coke.
Answer: Characteristics of coke:

• Coke is tough and hard.
• It is porous and has a black color.
• It is almost the purest form of carbon.

Uses: Coke helps in the manufacturing of steel and in the process of extracting many metals. It acts as a reducing agent.
In simple words: Coke is a tough, black, porous, nearly pure carbon. It's used to make steel and get metals from their ores.

Exam Tip: When describing a substance, always mention both its physical properties (characteristics) and practical applications (uses) for a comprehensive answer.

 

Question 8. Explain the process of formation of petroleum.
Answer: Petroleum is formed from tiny organisms that lived in the sea. When these organisms perished, their bodies sank and settled at the bottom of the ocean. These bodies then got covered with layers of sand and clay over time. Over millions of years, without air, and under very high temperature and pressure, these dead remains slowly transformed into petroleum and natural gas.
In simple words: Petroleum forms from tiny sea creatures that died, sank to the ocean floor, and were buried under layers of sand and clay for millions of years, turning into oil under heat and pressure.

Exam Tip: Highlight the role of "marine organisms," "absence of air," and "high temperature and pressure" as crucial factors in petroleum formation.

 

Question 9. The following Table shows the total power shortage in India from 1991-1997. Show the data in the form of a graph. Plot shortage percentage for the years on the y-axis and the year on x-axis.

Answer: The data from the table can be represented as a line graph, with years on the x-axis and shortage percentage on the y-axis.
In simple words: To make the graph, put the years on the bottom line (x-axis) and the shortage percentages up the side line (y-axis). Then, mark a dot for each year's percentage and draw lines connecting them to see the trend.

Exam Tip: When drawing graphs, always label both axes clearly, choose an appropriate scale, and plot points accurately before joining them to represent the trend correctly.