CBSE – Grade 8 – Science – Ch 03 – QA

Question 1: Explain the concept of natural resources and provide examples mentioned in the text.

Answer: Natural resources are materials used for basic needs, either found in nature or made by human efforts. Examples include air, water, soil, and minerals.

Question 2: Can all natural resources be utilized indefinitely? Provide reasons for your answer.

Answer: No, not all natural resources can be used forever. Some are exhaustible and can be depleted by human activities.

Question 3: Define Inexhaustible Natural Resources and provide examples. How do they differ from Exhaustible Natural Resources?

Answer: Inexhaustible Natural Resources are present in unlimited quantity in nature and are not likely to be exhausted by human activities. Examples include sunlight and air. They differ from Exhaustible Natural Resources, which have limited quantities and can be depleted by human activities, such as forests, wildlife, minerals, coal, petroleum, and natural gas.

Question 4: Explain the metaphorical use of “eatables in the container” as mentioned in the text. How does it relate to the availability of exhaustible natural resources?

Answer: The metaphor refers to the total availability of exhaustible natural resources like coal, petroleum, or natural gas. It signifies that each group may have a different consumption pattern, raising the question of whether earlier generations were too greedy or concerned about leaving resources for the coming generation(s).

Question 5: Elaborate on the formation process of coal as explained in the text. Include details about the origin of coal, the natural processes involved, and the conditions required for its conversion.

Answer: About 300 million years ago, dense forests in low-lying wetland areas were buried under soil due to natural processes like flooding. As more soil deposited over them, the forests were compressed, and with increasing temperature and pressure as they sank deeper, dead plants slowly converted to coal. This process, mainly involving carbon, is called carbonisation.

Question 6: Discuss the historical uses of coal mentioned in the text, including its role in railway engines and thermal power plants.

Answer: Coal was historically used in railway engines to produce steam for running them. Additionally, it is utilized in thermal power plants to generate electricity, showcasing its versatility as a fuel.

Question 7: Explore the characteristics of fossil fuels, particularly coal. Explain why coal is classified as a fossil fuel.

Answer: Fossil fuels, like coal, are formed from the dead remains of living organisms, in this case, plants. Coal is classified as a fossil fuel because it originated from the remains of vegetation and underwent the slow process of carbonisation.

Question 8: Reflect on the broader classifications of natural resources into Inexhaustible and Exhaustible categories. Provide real-world examples for each category.

Answer: Inexhaustible Natural Resources, like sunlight and air, are present in unlimited quantity and not likely to be exhausted by human activities. Exhaustible Natural Resources, such as forests, wildlife, minerals, coal, petroleum, and natural gas, have limited quantities and can be depleted by human activities.

Question 9: Consider the impact of natural resource consumption patterns on the environment. How can responsible consumption ensure the sustainability of these resources for future generations?

Answer: Responsible consumption can help ensure the sustainability of natural resources by avoiding overexploitation. It involves considering the environmental impact of resource usage, promoting conservation, and leaving resources for future generations.

Question 10: Analyze the significance of the discussion on earlier generations in the text. How does it contribute to the understanding of resource utilization and conservation?

Answer: The discussion on earlier generations raises questions about their greed or concern for future generations. It emphasizes the importance of balancing resource utilization and conservation to meet current needs while ensuring resources are preserved for the well-being of coming generations.

Question 11: Explain the process of burning coal in air and the main gas produced during this process.

Answer: When coal is heated in air, it burns and produces mainly carbon dioxide gas. This combustion reaction involves the reaction of carbon in coal with oxygen in the air.

Question 12: Describe the properties of coke and its significance in the manufacturing process.

Answer: Coke is a tough, porous, and black substance, almost pure carbon. It is used in the manufacture of steel and in the extraction of many metals. Its properties make it an ideal material for these processes due to its high carbon content and structural strength.

Question 13: What is coal tar, and how is it utilized in various industries?

Answer: Coal Tar is a black, thick liquid with an unpleasant smell, consisting of about 200 substances. It is used as starting materials for manufacturing various substances used in everyday life and industry, such as synthetic dyes, drugs, explosives, perfumes, plastics, paints, photographic materials, roofing materials, etc.

Question 14: Explain the shift from using coal-tar to bitumen in road metalling.

Answer: In modern times, bitumen, a petroleum product, is used instead of coal-tar for metalling roads. This shift is due to the improved properties of bitumen and its availability from petroleum refining, providing a more effective and durable solution for road construction.

Question 15: Elaborate on the process of obtaining coal gas and its applications in industries.

Answer: Coal gas is obtained during the processing of coal to get coke. It is used as a fuel in many industries situated near coal processing plants. The gas is a byproduct of coke production and finds application as a source of energy in various industrial processes.

Question 16: Discuss the historical use of coal gas for street lighting and its current applications.

Answer: Coal gas was initially used for street lighting in London in 1810 and later in New York around 1820. Nowadays, it is used primarily as a source of heat in industries rather than for lighting purposes due to advancements in lighting technologies.

Question 17: Explain the formation of petroleum and the role of high temperature and pressure.

Answer: Petroleum is formed from organisms living in the sea. When these organisms die, their bodies settle at the bottom of the sea, getting covered with layers of sand and clay. Over millions of years, absence of air, high temperature, and high pressure transform the dead organisms into petroleum and natural gas.

Question 18: Describe the geographical distribution of oil wells in India.

Answer: Oil is found in Assam, Gujarat, Mumbai High, and in the river basins of Godavari and Krishna in India. These regions are known for their significant oil reserves and contribute to the country’s oil production.

Question 19: Explain the reason behind the layer containing petroleum oil and gas being above that of water.

Answer: The layer containing petroleum oil and gas is above that of water because oil and gas are lighter than water and do not mix with it. This buoyancy effect causes them to remain above the water layer.

Question 20: Elaborate on the process of refining petroleum and its importance.

Answer: Refining of petroleum is the process of separating various constituents/fractions of petroleum in a petroleum refinery. It is crucial for obtaining different useful products such as petroleum gas, petrol, diesel, lubricating oil, paraffin wax, etc., each serving specific industrial and consumer purposes.

Question 21: Explain the various constituents of petroleum and their uses, as mentioned in the text.

Answer: The constituents of petroleum and their uses include Petroleum Gas in Liquid form (LPG) used as fuel for home and industry, Petrol utilized as motor fuel, aviation fuel, and solvent for dry cleaning, Kerosene employed as fuel for stoves, lamps, and jet aircrafts, Diesel serving as fuel for heavy motor vehicles and electric generators, Lubricating oil used for lubrication, Paraffin wax applied in ointments, candles, vaseline, etc., and Bitumen utilized in paints and road surfacing.

Question 22: Define the term ‘Petrochemicals’ and provide examples of substances obtained from petroleum and natural gas that fall into this category.

Answer: Petrochemicals are substances obtained from petroleum and natural gas. Examples include detergents, fibres such as polyester, nylon, acrylic, polythene, and other man-made plastics. Additionally, hydrogen gas obtained from natural gas is used in the production of fertilisers, specifically urea.

Question 23: Discuss the significance of petroleum, also known as ‘black gold,’ in commercial terms, as mentioned in the text.

Answer: Petroleum is referred to as ‘black gold’ due to its great commercial importance. It serves as a source of various valuable substances, including petrochemicals, which are essential in the manufacture of detergents, fibres, plastics, and more.

Question 24: Explain the characteristics and advantages of natural gas, especially in its compressed form (CNG).

Answer: Natural gas is easy to transport through pipes and is stored as Compressed Natural Gas (CNG) under high pressure. CNG is used for power generation and as a cleaner fuel for transport vehicles. Its advantage lies in its direct usability for burning in homes and factories through pipelines, and specific networks exist in places like Vadodara, Delhi, and other locations.

Question 25: Elaborate on the reserves of natural gas in India, including the regions where it has been found.

Answer: India has vast reserves of natural gas found in Tripura, Rajasthan, Maharashtra, and in the Krishna Godavari delta.

Question 26: Provide reasons, as stated in the text, why coal, petroleum, and natural gas cannot be prepared in the laboratory from dead organisms.

Answer: The formation of coal, petroleum, and natural gas is a very slow process, taking millions of years, and the specific conditions required for their formation cannot be artificially created in a laboratory.

Question 27: Discuss the exhaustible nature of fossil fuels and the need for judicious use, as emphasized in the text.

Answer: Fossil fuels, including coal and petroleum, are exhaustible resources formed from the dead remains of organisms over millions of years. The known reserves of these fuels will last only a few hundred years, and their burning contributes to air pollution and global warming. Hence, it is crucial to use these fuels judiciously and only when absolutely necessary to ensure a better environment and a reduced risk of global warming.

Question 28: Summarize the advice provided by the Petroleum Conservation Research Association (PCRA) to save petrol/diesel while driving.

Answer: The PCRA advises people to drive at a constant and moderate speed, switch off the engine at traffic lights or during waits, ensure correct tire pressure, and maintain regular vehicle maintenance.

Question 29: What are the primary products obtained from coal, as mentioned in the text?

Answer: The primary products obtained from coal are coke, coal tar, and coal gas.

Question 30: Enumerate the various substances derived from the refining of petroleum and their respective uses.

Answer: Substances obtained by refining petroleum include petroleum gas, petrol, diesel, kerosene, paraffin wax, and lubricating oil. These are used for various purposes, such as fuel, lubrication, and in the manufacturing of ointments, candles, and other products.

Question 31: Explain the limited nature of coal and petroleum resources, emphasizing the consequences of their excessive use.

Answer: Coal and petroleum are fossil fuels with limited reserves. Their formation took millions of years, but known reserves will last only a few hundred years. Excessive use of these fuels leads to air pollution, global warming, and environmental degradation. To mitigate these issues, it is essential to use these resources sparingly.

Question 32: Define the term ‘Petrochemicals’ and elaborate on their significance in the context of substances derived from petroleum and natural gas.

Answer: Petrochemicals refer to substances obtained from petroleum and natural gas. They are crucial in the manufacture of various products such as detergents, fibres (polyester, nylon, acrylic), polythene, and other man-made plastics. Additionally, hydrogen gas obtained from natural gas, a petrochemical, is used in fertiliser production (urea).

Question 33: Provide an overview of the advantages of using Compressed Natural Gas (CNG) as a fuel for transport vehicles.

Answer: CNG is advantageous as a fuel for transport vehicles because it is less polluting, serving as a cleaner fuel. Its high pressure storage and easy transport through pipelines make it a feasible and environmentally friendly option.

Question 34: Discuss the regions in India where natural gas reserves have been found, as mentioned in the text.

Answer: Natural gas reserves have been found in Tripura, Rajasthan, Maharashtra, and in the Krishna Godavari delta in India.