1. What are the different ways in which water gets contaminated?
Ans:
The different ways in which water gets contaminated are as follows:
i) Industrial waste: Harmful chemical waste released by industries into water bodies pollutes the water.
ii) Sewage waste: Waste materials from kitchens, laundry, and toilets flow into water sources, leading to contamination.
iii) Agricultural chemicals: Excessive use of pesticides and fertilizers in farming is carried to water bodies by rain or floods, causing water pollution.
2. At an individual level, how can you help reduce air pollution?
Ans:
We can take the following steps to help reduce air pollution:
i) Use public transport instead of personal cars whenever possible.
ii) Avoid burning garbage and ensure proper disposal of waste.
iii) For short distances, prefer walking or cycling instead of using vehicles.
iv) Regularly maintain household chimneys and vehicles to control emissions.
v) Use cleaner fuels such as LPG or CNG instead of diesel and petrol in vehicles.
3. Clear, transparent water is always fit for drinking. Comment.
Ans:
No, clear water is not always fit for drinking. Although it may appear clean, it could still contain harmful microorganisms and dissolved impurities that are not visible. Therefore, it is essential to purify water through methods like boiling or using water purifiers to ensure it is safe for consumption.
4. You are a member of the municipal body of your town. Make a list of measures that would help your town to ensure the supply of clean water to all its residents.
Ans:
To ensure the supply of clean water, the following measures should be taken:
a) Clean the area around water pipes to prevent contamination.
b) Ensure that the main water source is located in a clean environment and is properly maintained.
c) Implement chemical methods like chlorination to purify water.
d) Regularly monitor water quality to detect any contamination.
e) Educate the public about proper waste disposal and hygiene to avoid water pollution.
5. Explain the differences between pure air and polluted air.
Ans:
Pure air consists of 78% nitrogen, 21% oxygen, and 0.03% carbon dioxide, along with trace gases like methane, argon, ozone, and water vapors. Polluted air occurs when harmful substances such as sulphur dioxide, carbon monoxide, nitrogen dioxide, and particulate matter mix with the air, altering its natural composition and making it harmful to health.
6. Explain circumstances leading to acid rain. How does acid rain affect us?
Ans:
Acid rain is caused by the release of pollutants like sulfur dioxide and nitrogen dioxide, mainly from the burning of fossil fuels such as coal and diesel. These pollutants react with water vapor in the atmosphere to form sulfuric acid and nitric acid. These acids then fall as acid rain.
Effects of acid rain:
a) It destroys crops and vegetation.
b) It damages buildings, particularly those made of marble, like the Taj Mahal.
c) It harms aquatic life by altering the pH of water bodies.
7. Which of the following is not a greenhouse gas?
(a) Carbon dioxide
(b) Sulphur dioxide
(c) Methane
(d) Nitrogen
Ans:
The answer is (d) Nitrogen. Nitrogen is not a greenhouse gas. Greenhouse gases include carbon dioxide, methane, and others that trap heat in the atmosphere.
8. Describe the ‘Greenhouse Effect’ in your own words.
Ans:
The greenhouse effect refers to the process by which greenhouse gases such as carbon dioxide, methane, and water vapor trap heat in the Earth’s atmosphere. When solar radiation reaches the Earth, part of it is absorbed, and part is reflected back. Greenhouse gases trap the reflected heat, preventing it from escaping into space, thus warming the planet. While this is essential for maintaining life, excessive greenhouse gases lead to global warming.
9.Prepare a brief speech on global warming. You have to deliver the speech in your class.
Ans:
Good morning everyone,
Today, I want to talk about global warming. Global warming refers to the gradual increase in Earth’s average surface temperature, mainly due to human activities. The burning of fossil fuels has led to an increased concentration of greenhouse gases, such as carbon dioxide and methane, in the atmosphere. These gases trap heat from the Sun, preventing it from escaping back into space. As a result, our planet is warming, which leads to rising sea levels, melting glaciers, and more extreme weather events. It’s crucial that we reduce greenhouse gas emissions and adopt sustainable practices to protect our planet for future generations.
Thank you.
10. Describe the threat to the beauty of the Taj Mahal.
Ans:
The Taj Mahal is threatened by acid rain, which reacts with the marble, causing a powdery substance known as “marble cancer.” The rain, containing sulfuric and nitric acid, erodes the surface of the marble, leading to its deterioration. Additionally, soot particles from nearby industrial activities, like the Mathura oil refinery, are causing the marble to yellow, further damaging its appearance and structural integrity.
11. Why does the increased level of nutrients in the water affect the survival of aquatic organisms?
Ans:
An increase in nutrient levels in water bodies, especially nitrogen and phosphorus, causes excessive algae growth. This leads to eutrophication, where algae blooms consume a lot of oxygen. As the algae die, decomposers break them down, using up even more oxygen. This depletion of oxygen makes it difficult for fish and other aquatic organisms to survive, leading to their death.