NCERT
- A solar water heater cannot be used to get hot water on (a) a sunny day (b) a cloudy day Correct option is b) a cloudy day 2
- Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choices. Two exhaustible energy sources are as follows: Coal: It is produced from dead remains of plants and animals that remain buried under the ear... 1
- Name two energy sources that you would consider to be renewable. Give reasons for your choices. Two renewable sources of energy are : Sun: The energy derived from the Sun is known as solar energy. Solar energy is produced by the fusion... 1
- Hydrogen has been used as a rocket fuel. Would you consider it a cleaner fuel than CNG? Why or why not? Hydrogen gas is cleaner than CNG. CNG contains hydrocarbons. Therefore, it has carbon contents. Carbon is a form of pollutant present in CNG... 2
- Can any source of energy be pollution-free? Why or why not? No source of energy can be pollution-free. Every source of energy has some type of pollution. For example, the wastes of nuclear reaction ar... 1
- What are the advantages of nuclear energy? The advantages of nuclear energy are: Large amount of energy is produced per unit mass. It does not produce smoke. It is a clean energy. Fis... 1
- What is geothermal energy? Geothermal power plants use heat of the Earth to generate electricity. This heat energy of the Earth is known as geothermal energy. 1
- What are the limitations of the energy that can be obtained from the oceans? The forms of energy that can be obtained from the ocean are tidal energy, wave energy, and ocean thermal energy. There are several limitatio... 1
- What kind of mirror - concave, convex or plain - would be best suited for use in a solar cooker? Why? A concave mirror is used in a solar cooker as it uses heat of the sunlight to cook food. The mirror focuses all the incident sunlight at a p... 1
- How has the traditional use of wind and water energy been modified for our convenience? Earlier, the windmills were used to harness wind energy to do mechanical work such as lifting/drawing water from a well. Today, windmills ar... 1
- Why are we looking at alternate sources of energy? Fossil fuels which are traditionally used by human beings everywhere as an energy sources are non-renewable sources of energy. These sources... 1
- What are the disadvantages of fossil fuels? The disadvantages of fossil fuels are: Burning of coal and petroleum produces a lot of pollutants causing air pollution. Fossil fuels releas... 1
- If you could use any source of energy for heating your food, which one would you use and why? Natural gas can be used for heating and cooking food because it is a clean source of energy. It does not produce huge amount of smoke on bur... 1
- What is a good fuel? A good fuel produces a huge amount of heat on burning, does not produce a lot of smoke, and is easily available. 1
- What is a good source of energy? A good source of energy fulfils the following criteria: It produces a lot of heat per unit mass. It does a huge amount of work per unit mass... 1
- Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage? The damage to the ozone layer a cause for concern because: It causes skin darkening, skin cancer, ageing, and corneal cataracts in human bei... 1
- If all the waste we generate is biodegradable, will this have no impact on the environment? If all the waste generated would be biodegradable this will also create problem. As the numbers of decomposers will be quite low so wastes c... 1
- What are the problems caused by the non-biodegradable wastes that we generate? The problems caused by non-biodegradable wastes are: The cause biomagnification. They increase pollution. They make environment unclean. The... 1
- What is biological magnification? Will the levels of this magnification be different at different Biological magnification is defined as the phenomena of accumulation or increase in the concentration of some toxic substances at each troph... 1
- Will the impact of removing all the organisms in a trophic level be different for different trophic levels? Impact of removing all organisms of a trophic level is different for different trophic levels. For example, if we remove producers from a fo... 1
- What will happen if we kill all the organisms in one trophic level? If we kill all the organisms of one trophic level it will create an imbalance in the ecosystem. As an Example, In a food chain Grass → Dear... 1
- Which of the following are environment-friendly practices? (a) Carrying cloth-bags Correct option is d) All of the above 2
- Which of the following constitute a food-chain? (a) Grass, wheat and mango Correct option is b) Grass, goat and human 2
- Which of the following groups contain only biodegradable items? (a) Grass, flowers and leather The correct option is c) Fruit-peels, cake and lime-juice 2