POLLUTION OF AIR AND WATER: Questions and Answers CBSE/NCERT For Class 8th Science Chapter 18

POLLUTION OF AIR AND WATER: Questions and Answers CBSE/NCERT For Class 8th Science Chapter 18


Question: What makes hot water discharge into rivers a contributing factor in water pollution?

Ans: Factory wastewater often has a higher temperature than river water when it is released into the waterways. Due to the negative effects on aquatic plants and animals, the resulting rise in river water temperature is in and of itself a form of pollution.

Question: Water that has been filtered is clear of all suspended contaminants and thus potable. Do you completely agree? cite justifications.

Ans: Since only solid pollutants are filtered, I disagree with the claim that filtered water is potable because it may still contain germs.

Question: Give two suggestions for how to purify water at home.

Ans: By eliminating the bacteria in the water at home in the manner listed below, it can be rendered potable:

(i)Boiling: Boiling water for 15 to 20 minutes eliminates all microorganisms.

(ii) A purifier that uses ultraviolet light: Ultraviolet light is a special kind of light that kills microorganisms. It is utilized in several water purifiers that are now on the market.

Question: Nowadays, it is urged to utilize CNG in place of diesel in automobiles. Why?

Ans: The emission of hazardous gases like carbon monoxide and carbon particles is decreased using compressed natural gas, or CNG. All commercial vehicles in Delhi must now utilize CNG as a requirement. As a result, the city’s pollution has decreased.

Question: What exactly does a catalytic converter do?

Ans: New cars come equipped with a specific technology called a catalytic converter to reduce vehicle emissions. It can convert dangerous exhaust gases like nitrogen dioxide and carbon monoxide into safe levels of carbon dioxide and water.

Question: Waste has long been dumped in rivers. How is it that river contamination is now more concerning than it was before?

Ans: Due to the growing industrialization and human population, there is a significant volume of waste entering the waterways. As a result, the amount of waste released makes it impossible for the waste to decompose naturally.

Question: What causes eutrophication and what are its effects?

Ans: An excessive amount of fertilizer runoff into water sources causes an increase in the number of nutrients in the water. Through a series of events, this causes excessive plant growth and oxygen depletion in the water. Eutrophication is the term for the situation. The aquatic creatures and vegetation are negatively impacted.

Question: Describe four ways to conserve water.

Ans: The following are some strategies for conserving water:

(i)Conserve water at home and minimize waste.

ii) Using more effective irrigation techniques.

(iii)In factories, water is recycled and used multiple times before being disposed of.

(iv) Cleaning up industrial and sewage wastes before discarding them (v) Collecting rainwater to raise groundwater levels

Question: Describe SPM. What harm is caused by SPM pollution?

Ans: The term “suspended particulate matter,” or “SPM,” refers to tiny solid particles suspended in the air. SPM includes fine cement particles released by cement factories as well as unburned carbon particles released during fuel combustion or from vehicle exhausts. The finer of these particles is a key contributor to lung ailments since they cannot be filtered by the hair in our noses. Additionally, they land on plants and obstruct photosynthesis.

Question: What makes carbon monoxide such a hazardous pollutant?

Ans: One of the most harmful pollutants is carbon monoxide. It has terrible toxicity. As it combines with the blood, oxygen cannot be carried by it. Lack of oxygen even has the potential to be fatal.

Question: Plants require carbon dioxide in the air to produce food, thus it is necessary. When does something start to pollute? What harm does it inflict?

Ans: Every time fuel is used in buildings like homes or industries or vehicles, carbon dioxide is created. Carbon dioxide is not pollution in and of itself. However, the amount of carbon dioxide in the air is rising since so much fuel is being burned today. Deforestation also results in fewer trees, which use carbon dioxide from the atmosphere during photosynthesis. The amount of carbon dioxide in the air likewise rises as a result of this. The heat from the sun is trapped by too much carbon dioxide in the atmosphere. The term “greenhouse effect” refers to this. Global warming is the term used to describe the rise in the earth’s temperature that is thought to be caused by this.

Question: Describe four techniques to conserve air.

Ans: Here are a few strategies for preserving air: To lower air pollution, planting trees is crucial.

Use of smokeless stoves with efficient designs.

Utilizing smokeless fuels like LPG and CNG.

Equipping automobiles with a unique mechanism known as a catalytic converter to reduce vehicle emissions

Preventing the release of waste gases into the environment by using electrostatic precipitators to remove solid particles, such as carbon, from the gases.


Question: How are water bodies impacted by the overuse of pesticides and fertilizers?

Ans: Rain causes fertilizers and chemicals to wash into water sources. They also contaminate groundwater through seepage into the earth. Fertilizer runoff into water sources increases the growth of algae in the water, which depletes the water’s dissolved oxygen. When algae perish, they provide food for bacteria and other decomposers, who also use the dissolved oxygen, further lowering the oxygen content. Additionally, its dense growth prevents sunlight from reaching the water. The aquatic flora and animals are negatively impacted by this.

Question: Talk about the various ways we can purify water by eradicating bacteria.

Ans: Any of the following techniques can be used to make water potable:

1. Boiling: Killing all bacteria requires boiling water for 15 to 20 minutes.

2. Ultraviolet light: Germs are destroyed by this particular form of light.

3. Reverse osmosis: A semi-permeable membrane allows water to pass through it. It features tiny pores that allow water to pass through but not solid contaminants or bacteria.

4. Chlorination: By adding chlorine to water in the form of bleaching powder or chlorine tablets, bacteria can be killed.

Question: How is the water made potable at the waterworks?

Ans: The waterworks purify the water before it is distributed to our homes. These are the procedures used:

1. To eliminate bigger solid impurity particles, sedimentation and decantation are first performed.

2. To further separate the smaller particles by making them heavier so they settle down, alum is next added to the water.

3. Sand filters are used to filter the water after that.

4. Chlorination, or the addition of chlorine to the water, kills germs.

Question: List the primary air contaminants and describe each one’s negative impacts.

Ans: 1. The following are the primary air contaminants and their effects: Small solid particles suspended in the air are known as suspended particulate matter or SPM. Since our nose hair cannot filter the smaller of these particles, they are a substantial contributor to lung ailments.

2. Carbon monoxide: One of the most hazardous pollutants is carbon monoxide. It has terrible toxicity. As it combines with the blood, oxygen cannot be carried by it.

3. Too much carbon dioxide: Too much carbon dioxide in the atmosphere traps solar heat. The earth’s temperature is thought to rise as a result of this. The ice in the polar areas may melt on a vast scale as a result of this, and ocean water may also expand. This may ultimately result in coastal areas being flooded by seawater.

4.Sulfur dioxide is harmful, as is nitrogen dioxide. We experience lung damage. Acid rain is created when this gas and water combine to make sulphuric acid. Additionally toxic is nitrogen dioxide. It harms the lungs and irritates the eyes.

5. Chlorofluorocarbons (CFCs): These substances have the potential to destroy the ozone layer in the atmosphere, increasing the number of UV sun rays that reach the planet. The skin and eyes are harmed by this light.

6. Lead: Compounds containing lead can damage the brain and create mental disorders, among other issues.

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