Class 8 Science
Question 1: What is air pollution?
Answer: Contamination of air to make it harmful for living beings is called air pollution.
Question 2: What are the natural causes of air pollution?
Answer: Smoke and dust from forest fire and volcano pollute the air are the natural causes of air pollution.
Question 3: What is the benefit of ozone layer?
Answer: Ozone layer prevents harmful ultraviolet radiations from the sun from entering our atmosphere.
Question 4: What is smog?
Answer: A mixture of smoke and fog is called smog.
Question 5: What is acid rain?
Answer: When rainwater comes along with acid, it is called acid rain.
Question 6: What is global warming?
Answer: Overall increase temperature of earth is called global warming.
Question 7: What is water pollution?
Answer: Contamination of water to make it harmful for living beings is called water pollution.
Question 8: What is potable water?
Answer: Water which is fit for drinking is called potable water.
Question 9: How does boiling purify water?
Answer: Boiling purifies water by killing germs in water.
Question 10: What is the full form of three Rs?
Answer: Reduce, Reuse and Recycle
Question 1: How do automobiles pollute air?
Answer: Automobiles usually have internal combustion engines which use petrol or diesel as fuel. Combustion of petrol or diesel results in emission of many polluting gases; like carbon dioxide, carbon monoxide, sulphur dioxide, nitrogen dioxide, etc. Moreover, minute particles are also emitted from automobile engines. Thus, automobiles end up polluting the air.
Question 2: How are dust particles added in air?
Answer: There are many sources of dust particles, e.g. stone quarries, mines, power plants, construction sites, etc.
Question 3: Write a short note on ozone layer.
Answer: Ozone layer is a protective layer in the atmosphere. It contains a higher amount of ozone than any other layer of the atmosphere. However, compared to other gases; ozone still forms a negligible part of air in ozone layer. This layer prevents harmful ultraviolet radiations from the sun from entering our atmosphere. Ultraviolet radiations can cause skin cancer in humans and animals, and is also harmful for plants. Any damage to the ozone layer can be highly detrimental to the living beings.
Question 4: Write a short note on acid rain.
Answer: Oxides of sulphur and nitrogen mix with rainwater to create acid rain. Acid rain can be harmful for living beings and also for non-living things. Acid rain corrodes the outer surface of buildings. This has caused the Taj Mahal becoming pale.
Question 5: What is greenhouse effect? What is the harm of greenhouse effect?
Answer: Greenhouse gases, like carbon dioxide and methane trap solar radiation and thus increase atmospheric temperature. This is called greenhouse effect. Greenhouse effect results in global warming.
Question 6: What are the effects of global warming?
Answer: Global warming is causing melting of icebergs and glaciers. It is resulting in increased cases of flash floods and a rise in sea level. It is also causing drastic changes in weather patterns.
Question 7: What is eutrophication?
Answer: Enrichment of water body with nutrients is called eutrophication. It happens because of excess amount of chemicals in water. This results in proliferation of algae and other plants in water bodies with stagnant water. Once these plants die, they are consumed by decomposers. The process of decomposition utilizes most of the oxygen from water. This results in deficiency of oxygen for aquatic animals.
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