NIOS Class 12 Environmental Science Chapter 28B
INTEXT QUESTIONS 28.1
1. Mention the method of coal formation.
Ans: Plant material of swamps died and accumulated under water many centuries ago, forming peat. Sediments of sand and soil were deposited over the peat. The weight of sediments and heat from the earth change peat into soft coal (bituminous coal) to hard coal (anthracite).
2. State the major uses of coal.
Ans: Coal is used as a fuel for domestic use. It is used in locomotive engines and various types of furnaces in the industries. It is used as a fuel in thermal power plants for the generation of electricity.
INTEXT QUESTIONS 28.2
1. Which are the major fractions obtained from the distillation process of crude oil?
Ans: The products or fractions obtained from crude oil distillation are gases, gasoline (petrol), aviation fuel, kerosene, diesel oil, naptha, grease, and asphalt.
2. What is the composition of conventional natural gas? Mention any one of its advantages as a fuel?
Ans: Natural gas is a mixture of methane, with small amounts of heavier hydrocarbons such as ethane and butane. Advantages of natural gas are :
- a) It is used directly for cooking purposes at home.
- (b) It burns smokeless and does not produce any poisonous gases on burning.
INTEXT QUESTIONS 28.3
1. What is meant by radioactive pollution?
Ans: The advantage of nuclear material for energy generation is that it produces very little pollution, it requires less mining as nuclear fuel is a concentrated form of energy, and the cost of transportation of nuclear fuel is lower than that for an equivalent amount of coal.
2. Distinguish between nuclear fission and nuclear fusion reactions.
Ans: Nuclear fission occurs because atoms of radioactive minerals contain nuclei that are unstable and break or split apart, releasing energy. Nuclear fusion involves uniting two small atoms to form a large atom with the release of an enormous amount of energy.
3. What advantage does nuclear material have as an energy source over coal and oil?
Ans: Radioactive elements, if not disposed of properly, cause disintegration in soil and water, causing radioactive pollution which has long-lasting effects on human health and the environment.
TERMINAL EXERCISE
1. What actions can you take at a personal level to reduce consumption of fossil fuels?
Ans: By using electric vehicles, switching to solar power for electricity, natural gas for cooking, solar energy for water heating, etc, consumption of fossil fuels can be reduced.
2. How were fossil fuels formed?
Ans: Fossil fuels represent stored solar energy captured by plants in the past geological times. Coal, petroleum, and natural gas are called fossil fuels, as they are the remains of prehistoric plants, animals, and microscopic organisms that lived millions of years ago. These remain under the effect of intense heat and pressure underneath the earth’s crust over long geological time and are transformed into fossil fuels.
3. Discuss the advantages and disadvantages of nuclear energy.
Ans:
Advantages
- The advantage of using nuclear material for energy generation instead of coal and oil is that it produces very little pollution.
- It requires less strip-mining as nuclear fuel has a highly concentrated form of energy.
- Moreover, the cost of transportation of nuclear fuels is much lower than that for coal and oil required for the generation of an equivalent amount of energy.
Disadvantages
- The major problems associated with the generation of nuclear power are disposal of nuclear waste, contamination of environment with long lasting radioactive materials (radioactive pollution) thermal pollution, health effects from exposure to low levels of radiation, limited supplies of uranium ore, high construction and maintenance costs, questionable reactor safety, human or technical error that could result in a major accidents and vulnerability to sabotage, developing nuclear weapons by processing reactor waste.
4. Speculate which one of the fossil fuels will run out first.
Ans: Petroleum is the fossil fuel that is likely to run out first, as the available reserve is 2000 billion barrels. The consumption of petroleum products is rising worldwide. In India, the demand has risen from 57 million tonnes in 1991-1992 to 107 million tonnes in the year 2000. ‘The India Hydrocarbon Vision 2025’, gives the projected need for petroleum products for India to be 368 million tonnes by 2025. With this growing population and the requirements to meet it is soon to be over.
5. Discuss the importance of energy consumption to society. What major concerns does it basis?
Ans: Fossil fuels are one of the most important mineral energy sources. These are finite energy resource that means they are non-renewable resources, and once consumed, they are lost forever. Since society needs energy to sustain in various levels, it requires a huge amount of energy. As fossil fuels are non-renewable, people must look for other sources of energy to meet the growing requirements. Thus, there are other options such as solar energy, hydropower, nuclear energy, wind energy, etc., to generate electricity.
However, each of these alternative sources of energy has its drawbacks that has huge negative impact on society. The best way to move forward is to consume less energy and rely more on sustainability by using renewable sources that are economical and less polluting to the environment.
6. Describe the pros and cons of the following types of fossil fuels.
i) Coal
ii) Oil
iii) Natural gas
Ans:
i) Coal
- Pros: The coal is used as a source of energy for domestic uses, locomotive engines, various types of furnaces in the industries, thermal power generation, extraction of metals and minerals, production of gas, tar, etc.
- Cons: Its mining causes soil erosion, destruction of natural ecosystems, pollution, etc.
ii) Oil
- Pros: Some of the products of oil distillation are called petro-chemicals, which are used as raw material for the manufacture of pesticides, plastics, synthetic fibers, paints, and medicines, etc.
- Cons: Extraction of oil and gas may cause sinking of land or subsidence. Typically, for every barrel of oil productio,n ten barrels of brine are also extracted, which brine can contaminate fresh water aquifers if the casing lining the well is missing or corroded.
iii) Natural gas
- Pros: Natural gas is a clear and environmentally friendly fuel and is used directly for cooking purposes in homes. It can be supplied directly to the homes and factories through a network of underground pipelines, thus eliminating the need for additional storage and transport. Natural gas burns with a smokeless flame and, on burning, does not produce any poisonous gas or pollute the environment friendly gas.
- Cons: Leakage of natural gas from pipelines, storage tanks, and distribution tanks is a potential cause of explosion. Methane, being a major component of natural gas, happens to be a greenhouse gas, and its leakage contributes to global warming.
7. Describe the environmental degradation caused by the use of fossil fuels in the 20th century.
Ans: Coal is the most abundant fossil fuel on earth, but there are problems associated with its mining, transportation, and use. Coal is mined from both surface mines and underground mines.
(a) Surface mining
- Surface mining disrupts and drastically changes the natural landscape and destroys the natural vegetation and the habitat of many species, some of which may already be endangered.
- Mining operations cause serious problems of air and noise pollution.
- Surface mining may also cause soil erosion and silt loading (the discharge of silts into streams) and nallas that disrupt and pollute the aquatic ecosystems, as well as groundwater in places where aquifers are located near or associated with coal seams.
(b) Underground mining
- Underground mining may cause collapse or land subsidence in the mining areas during or after mining operations are over.
- In the case of some mines, acid mine drainage from the mine waste and OBD piles polluted long stretches of streams.
- Coal fires in underground mines may happen, which naturally caused give out much smoke, and hazardous fumes cause several respiratory disease to people living nearby.
- Apart from these problems, burning of coal in thermal power plants for gthe eneration of electricity and in industry is the prime source of air pollution.
8. Explain fusion and fission and differentiate them.
Ans:
- i) Nuclear fission – In this process, the nucleus of a heavy atom, namely of uranium (U235) or plutonium (P239, breaks apart into smaller fragments, releasing an enormous amount of energy.
- ii) Nuclear fusion – In this process, small nuclei like those of isotopes of hydrogen, namely deuterium and tritium, etc., fuse or join together to form heavier nuclei, releasing vast amounts of energy.
9. Give your view on “Nuclear power and energy source”.
Ans: Nuclear power is a fuel mineral resource, and so is an exhaustible resource; however, only a small quantity can generate a large amount of electricity. Nuclear energy is the energy of the atomic nucleus. Radioactive minerals are used to generate nuclear energy through high technological methods.
A radioactive mineral generates nuclear energy through fission. Whenever a neutron strikes a nucleus of U-235, energy is released, krypton and barium are produced, and several neutrons are released. These new neutrons may strike other atoms of U-235 to produce a chain reaction.
In the reactor of a nuclear power plant, the rate of nuclear chain reaction is controlled, and the heat generated is used to produce high-pressure steam, which spins the turbine that generates electricity. Heat produced here is carried away by water coolant and transferred by way of a heat exchanger to the water in a steam-generating unit. The steam produced powers a turbine that produces electricity. Cooling water is used to condense the steam after it has gone through the turbine.
Additional Study Materials
Chapter 27B Importance of Energy in Society
