NIOS Class 12 Environmental Science Chapter 27B
INTEXT QUESTIONS 27.1
1. How would you define energy?
Ans: Energy is the capacity to do work.
2. What is a gram calorie?
Ans: A gram Calorie (c): It is the amount of heat required to raise the temperature of one gram of water through one degree centigrade (from 14.5 °C to 15.5 °C) and is the unit in which the energy value of food or any other organic matter is expressed. However, it is now being replaced by joules.
3. What is the SI unit of energy?
Ans: SI unit of energy is Joule (J). It is the work done when a force of one Newton displaces the point by one metre.
4. State the First and the Second law of thermodynamics.
Ans:
- First law: energy can neither be created nor destroyed but can only change from one form to another.
- Second law states that in every transformation, some energy is always lost in the form of heat.
INTEXT QUESTIONS 27.2
1. Define the terms renewable energy sources and non-renewable energy sources.
Ans: Renewable energy is the term used to describe energy that comes from sources whose supplies are regenerative and virtually inexhaustible. Non-renewable energy resources have a limited amount of stock available, and the energy resources cannot be recreated in a short period of time.
2. What are the various ways solar energy can be used?
Ans: Solar energy can be used in a variety of ways, such as heating homes and heating water (using a solar cooker to prepare food). And produce electricity. Solar power includes active, passive, and photovoltaic technologies and practices.
- Active and passive solar technologies use the sun’s energy for cooking, space heating, and water heating.
- Photovoltaic (solar cells) convert solar energy directly into electricity.
- The simplest solar cells are used to energise watches and calculators and the like, while more complex systems of large panels of solar cells can light houses, provide power to spacecraft and satellites.
3. List the various sources of renewable and non-renewable energy.
Ans:
- Renewable energy sources – Solar, wind, hydropower, geothermal, ocean, thermal energy, biomass, hydrogen.
- Non-renewable energy sources – Coal, gas, oil, or petroleum.
4. Why is hydrogen known as a clean energy source?
Ans: Hydrogen produces clean energy and pure water without causing any pollution.
5. How is coal formed in nature?
Ans: Coal is formed from trees that grew millions of years ago in swampy areas. The trees sank to the bottom of the swamps when they died. They did not rot fully as there was no air. Many layers of sand and mud got deposited on these plant remains for years, and the plant matter turned into coal under pressure and heat.
TERMINAL EXERCISE
1. What do you understand by bio-energy? Describe the various types and ways of using biomass energy.
Ans: Biomass energy or bioenergy is the energy from organic matter such as firewood, twigs, dead plant parts, cattle dung, livestock manure, and dead animal matter.
- Biomass fuels are renewable because the raw materials can be produced simply by growing more crops or collecting more organic waste.
- Biogas can be produced from cattle dung, human faeces, and other organic waste by a process called “anaerobic digestion” in a biogas plant.
- The digested leftover material, which comes out of the biogas plant in the form of slurry, is a valuable by-product that can be used as organic manure in agricultural fields.
- Produce ethanol, a liquid alcohol fuel, from biomass.
2. Define the first and second laws of thermodynamics.
Ans:
- First law: energy can neither be created nor destroyed but can only change from one form to another.
- Second law states that in every transformation, some energy is always lost in the form of heat.
3. Prepare a list of renewable and non-renewable energy resources.
Ans:
- Renewable energy sources – Solar, wind, hydropower, geothermal, ocean, thermal energy, biomass, hydrogen.
- Non-renewable energy sources – Coal, gas, oil, or petroleum.
4. What is a fuel cell? Which fuel is used to propel rockets?
Ans: Fuel cells are devices that directly convert hydrogen into electricity. Hydrogen has been used in NASA’s space program as fuel since the 1970s to propel rockets and now the space shuttle into orbit, and in fuel cells that provide heat, electricity, and drinking water for astronauts.
5. What type of conditions are necessary for biogas generation?
Ans: Anaerobic conditions.
6. What is the average composition of biogas?
Ans: It contains about 55 to 75% methane, which is inflammable and can be used for cooking, lighting, heating, or producing electricity.
7. Why is hydrogen considered a clean energy source?
Ans: Hydrogen as a fuel is high in energy and a very promising clean fuel. A fuel cell converts hydrogen (produced and stored) and oxygen from the air into electricity. A machine that burns pure hydrogen produces energy and pure water without causing any pollution.
8. What is the ultimate source of energy in coal and petroleum?
Ans: Solar energy is the ultimate source of energy in coal and petroleum.
9. Describe the process of coal and petroleum formation.
Ans: Fossil fuels were formed before and during the time of the dinosaurs when plants and animals died.
Their decomposed remains gradually changed over the years to form coal, oil, and natural gas.
- Oil and natural gas are formed by complex decay processes from microscopic life forms called phytoplankton.
- When they died, they sank to the sea floor and were buried and slowly hardened into rocks.
- Heat from the earth’s interior and the weight of the overlying rocks gradually changed the energy-containing substances in the buried phytoplankton into liquid hydrocarbons and gases.
- These molecules, being light and mobile, migrated upwards through the rock but eventually became trapped beneath impermeable rock structures in the earth’s crust.
10. State the reasons for increasing emphasis on developing renewable sources of energy.
Ans: There is a growing emphasis on promoting the use of renewable energy sources.
- It is done to reduce our dependence on fossil fuels because they will be exhausted soon.
- The growing use of fossil fuels has increased the amount of carbon dioxide in the atmosphere, leading to global warming and climate change.
- Fossil fuels are a non-renewable and finite resource, and we can’t use them forever.
11. Which type of power or energy causes no pollution?
Ans:
- A machine that burns pure hydrogen produces energy and pure water, causing no pollution.
- Solar energy is another option for clean energy.
- Geothermal energy
- Wind energy
- Wave eenrgy
Additional Study Materials
- Chapter 27A Global Circulation of Water
- Chapter 28A Groundwater Resources
- Chapter 29A Freshwater Resources
- Chapter 30A Methods of Water Harvesting
- Chapter 31A Water Conservation at Different Levels
