2. Give short answer.
(i) List two main sources of acid rain.
Answer: The two main sources of acid rain are:
1. Burning of Fossil Fuels: Power plants and industrial processes release sulfur dioxide (SO₂) and nitrogen oxides (NOx) into the atmosphere.
2. Vehicle Emissions: Cars, trucks, and buses release nitrogen oxides (NOx) and some sulfur dioxide (SO₂) from the combustion of gasoline and diesel. These gases react with water, oxygen, and other chemicals in the atmosphere to form acidic compounds.
(ii) List four human activities which contribute to air pollution.
Answer: Four human activities contributing to air pollution:
1. Burning of Fossil Fuels: For electricity generation, transportation, and industrial processes.
2. Industrial Processes: Factories release pollutants like SO₂, NOx, VOCs, and particulate matter.
3. Agricultural Activities: Use of fertilizers releases ammonia; livestock produces methane.
4. Waste Disposal: Open burning of garbage and landfills release toxic fumes and methane.
(iii) What is the importance of catalytic converters?
Answer: Catalytic converters are important because they reduce the toxicity of exhaust gases from vehicles. They convert harmful pollutants like carbon monoxide (CO), unburnt hydrocarbons (HC), and nitrogen oxides (NOx) into less harmful substances like carbon dioxide (CO₂), water (H₂O), and nitrogen (N₂). This significantly reduces air pollution from automobiles.
(iv) What is the role of automobile in air pollution?
Answer: Automobiles play a major role in air pollution by emitting:
Carbon Monoxide (CO): From incomplete combustion. Nitrogen Oxides (NOx): From high-temperature combustion. Unburnt Hydrocarbons (HC): From incomplete combustion. Particulate Matter (PM): From diesel engines. Carbon Dioxide (CO₂): A greenhouse gas. These emissions contribute to smog, acid rain, and global warming.
(v) Define global warming.
Answer: Global warming is the long-term increase in the Earth's average surface temperature due to the enhanced greenhouse effect. It is primarily caused by human activities that release greenhouse gases (e.g., CO₂, CH₄, N₂O) into the atmosphere. These gases trap heat, leading to climate change, rising sea levels, and extreme weather events.
3. Describe sources of air pollutants.
Answer: Sources of air pollutants include:
Natural Sources: Volcanic eruptions (SO₂, ash), forest fires (CO, CO₂, smoke), dust storms (particulate matter), and biological decay (methane). Anthropogenic (Human) Sources:
Stationary Sources: Power plants, factories, and residential heating (burning coal, oil, gas). Mobile Sources: Cars, trucks, buses, airplanes, and ships. Agricultural Sources: Fertilizers, pesticides, and livestock. Waste Management: Landfills and open burning.
4. Describe acid rain and its effects.
Answer: Acid rain is precipitation (rain, snow, fog) with a pH lower than 5.6, caused by the release of SO₂ and NOx into the atmosphere. These gases react with water vapor to form sulfuric and nitric acids. Effects:
Aquatic Ecosystems: Acidifies lakes and rivers, killing fish and aquatic life. Soil: Leaches essential nutrients and releases toxic aluminum. Forests: Damages leaves and roots, stunting growth. Buildings and Monuments: Corrodes stone (marble, limestone) and metal structures. Human Health: Respiratory problems from inhaling acid aerosols.
5. Describe global warming.
Answer: Global warming is the gradual increase in the Earth's average temperature due to the accumulation of greenhouse gases. These gases trap heat from the sun, causing the planet to warm. The main greenhouse gases are carbon dioxide (CO₂), methane
(CH₄), nitrous oxide (N₂O), and water vapor. Human activities like burning fossil fuels, deforestation, and industrial processes have significantly increased the concentration of these gases, intensifying the natural greenhouse effect and leading to climate change.
6. What is ground level ozone. Explain.
Answer: Ground-level ozone (O₃) is a secondary pollutant formed when nitrogen oxides (NOx) and volatile organic compounds (VOCs) react in the presence of sunlight. It is a major component of photochemical smog. Unlike stratospheric ozone, which protects us from UV radiation, ground-level ozone is harmful to human health (causing respiratory problems) and damages vegetation and materials.
7. Why is global warming often referred to as the greenhouse effect? Justify your answer.
Answer: Global warming is often referred to as the greenhouse effect because the mechanism is similar to how a greenhouse works. In a greenhouse, glass panels trap heat inside, warming the plants. Similarly, greenhouse gases (CO₂, CH₄, etc.) in the atmosphere trap heat from the sun, preventing it from escaping back into space. However, the enhanced greenhouse effect, caused by human activities, is leading to excessive warming, which is global warming. Thus, the term is used because the gases act like the glass of a greenhouse.
8. Sulphur dioxide is a common pollutant from burning coal. State two effects caused by this pollutant.
Answer: Two effects of sulfur dioxide (SO₂) pollution:
1. Acid Rain: SO₂ reacts with water vapor and oxygen in the atmosphere to form sulfuric acid, which falls as acid rain, damaging ecosystems, soil, and buildings.
2. Respiratory Problems: Inhaling SO₂ irritates the respiratory system, causing coughing, wheezing, and aggravating
conditions like asthma and bronchitis.
