NCERT Class 9 Science Chapter 14 Natural Resources

Chapter 14 Natural Resources

Intext Questions
Question 1: How is our atmosphere different from the atmospheres on Venus and Mars?
Answer: Air is a mixture of many gases like nitrogen, oxygen, carbon dioxide and water vapour. The composition of air is the result of life on Earth. In planets such as Venus and Mars, where no life is known to exist, the major component of the atmosphere is found to be carbon dioxide which constitutes up to 95-97% of the atmosphere.

Question 2: How does the atmosphere act as a blanket?
Answer: The atmosphere covers the Earth, like a blanket. The atmosphere keeps the average temperature of the Earth fairly steady during the day and the whole year. The atmosphere prevents the sudden increase in temperature during the daylight hours. And during the night, it slows down the escape of heat into outer space. 

Question 3: What causes winds?
Answer: The movement of air is called wind. The heating of air is the reason behind wind. On being heated, the air rises up, and low pressure is created. The air in high pressure takes the place of the low-pressure region resulting in the wind.

Question 4: How are clouds formed?
Answer: When water bodies are heated during the day, a large amount of water evaporates and goes into the air. Some amount of water vapour also get into the atmosphere because of various biological activities. This air also gets heated. The hot air rises up carrying the water vapour with it. As the air rises, it expands and cools. This cooling causes the water vapour in the air to condense in the form of tiny droplets to form clouds.

Question 5: List any three human activities that you think would lead to air pollution.
Answer: Three human activities that leads to air pollution are
• Burning of fossil fuels
• Smoke released from vehicles
• Fumes from chemical plants

Question 6: Why do organisms need water?
Answer: All cellular processes take place in a water medium. All the reactions that take place within our body and within the cells occur between substances that are dissolved in water. Substances are also transported from one part of the body to the other in a dissolved form. Hence, organisms need to maintain the level of water within their bodies in order to stay alive. Terrestrial life-forms require fresh water for this because their bodies cannot tolerate or get rid of the high amounts of dissolved salts in saline water. Thus, water sources need to be easily accessible for animals and plants to survive on land.

Question 7: What is the major source of fresh water in the city/town/village where you live?
Answer: Rainfall, Tube-well, ponds, rives etc.

Question 8: Do you know of any activity which may be polluting this water source?
Answer: Some activities which may be polluting fresh water are:
• Littering garbage in or near water bodies
• Factory waste
• Mixing of fertilizers and pesticides from farms into water bodies

Question 9: How is soil formed?
Answer: Over long periods of time, thousands and millions of years, the rocks at or near the surface of the Earth are broken down by various physical, chemical and some biological processes. This lead to the formation of fine particles of soil.

Question 10: What is soil erosion?
Answer: Soil erosion is the natural process in which the topsoil of a field is carried away by physical sources such as wind and water.

Question 11: What are the methods of preventing or reducing soil erosion?
Answer: Methods of preventing or reducing soil erosion are
• Planting more trees
• Contour ploughing and terrace farming in hilly areas
• Preventing excessive grazing

Question 12: What are the different states in which water is found during the water cycle?
Answer: Water is found in three states during water cycle: Solid, Liquid and Gas.

Question 13: Name two biologically important compounds that contain both oxygen and nitrogen.
Answer: Nucleic Acids (DNA and RNA) and amino acid are two biologically important compounds that contain both oxygen and nitrogen.

Question 14: List any three human activities which would lead to an increase in the carbon dioxide content of air.
Answer:
• Burning of fossil fuels
• Deforestation
• Using CFC products like refrigerator, ACs etc.

Question 15: What is the greenhouse effect?
Answer: Greenhouse gases like carbon dioxide, ozone, nitrous oxide, methane etc. trap the sun’s radiation and do not allow it to go back. This causes the warming of the atmosphere, resulting in the greenhouse effect.

Question 16: What are the two forms of oxygen found in the atmosphere?
Answer: Diatomic form (O₂) and Triatomic form (O₃)

Exercise Questions
Question 1: Why is the atmosphere essential for life?
Answer: It keeps the average temperature of the Earth. It contains all the gases like oxygen which are essential for sustaining life on the Earth. Ozone layer present in the atmosphere prevents harmful UV rays from reaching the Earth.

Question 2: Why is water essential for life?
Answer: All cellular processes take place in a water medium. All the reactions that take place within our body and within the cells occur between substances that are dissolved in water. Substances are also transported from one part of the body to the other in a dissolved form. Terrestrial life-forms require fresh water because their bodies cannot tolerate or get rid of the high amounts of dissolved salts in saline water. 

Question 3: How are living organisms dependent on the soil? Are organisms that live in water totally independent of soil as a resource?
Answer: All living organisms on the earth, directly or indirectly, are dependent on soil for a living. Plants obtain water and minerals through the soil and are thus able to prepare their food. Other organisms that live in water are not totally independent of soil because the microbes growing on the soil in water are the primary producers. Primary producers are the main element of the food chain. Various microbes present in soil help in the decomposition of dead organisms in water, which helps in returning the nutrients and elements back to the water.

Question 4: You have seen weather reports on television and in newspapers. How do you think we are able to predict the weather?
Answer: Weather is dependent on various elements, like temperatures, humidity, rainfall, wind speed etc. and by using various scientific instruments, we are able to forecast the weather, on the basis of the data collected by the meteorologists.

Question 5: We know that many human activities lead to increasing levels of pollution of the air, water-bodies and soil. Do you think that isolating these activities to specific and limited areas would help in reducing pollution?
Answer: Human activities like deforestation, manufacturing etc. are main reasons for pollution of the air, water and soil. Various means of spreading pollutants are air, water, soil. By limiting human activities in limiting places will help in reducing pollution.

Question 6: Write a note on how forests influence the quality of our air, soil and water resources.
Answer:
• Forest influences air
→ Helps in purifying of air
→ Take carbon-dioxide and provide oxygen
→ Helps in maintaining temperature by reducing the effect of greenhouse gases

• Forest influences soil
→ Prevent soil erosion
→ Adds nutrients to soil by decomposing various organisms like plants, animals

• Forest influences water
→ Responsible for maintaining water-cycle
→ Helps in bringing rain
→ Maintain ground water level