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Class 9 General science chapter 14 Natural resources answers pdf |
class 9
General science
chapter 14
Natural
resources
PAGE 193
1.How is our atmosphere different from the atmospheres on Venus and Mars?
Answer: Earth’s atmosphere is different from those of Venus and Mars. This difference lies essentially in their compositions. Earth's atmosphere is a mixture of nitrogen (79%), oxygen (20%), and a small fraction of carbon dioxide, water vapours and other gases. This makes the existence of life possible on Earth. However, the atmospheres on Venus and Mars mainly consist of carbon dioxide. The amount of carbon dioxide on these planets can range from 95% to 97%.
2. How does the atmosphere act as a blanket?
Answer: The atmosphere acts as a blanket by performing the following functions:
(a) It keeps the average temperature of the Earth fairly constant during day tme and even during the course of whole year.
(b) It prevents a sudden increase in the temperature during day time.
(c) It slows down the escape of heat from the surface of the Earth into outer space during night time.
3. What causes winds?
Answer: The uneven heating of the earth’s surface is the main cause for the winds. On being heated more the air raises up and hence low pressure is created. Hence the air in high pressure occupy the low-pressure region causing the wind.
4: How are clouds formed?
Answer: During day time, on being heated, a large amount of water evaporates from various water bodies and goes into the air. A part of this water vapour also reaches the atmosphere through biological activities such as transpiration and respiration. This causes the air in the atmosphere to heat up.
When this heated air rises, it expands and cools, which results in the condensation of water vapour forming water droplets. The presence of dust and other suspended particles in air also facilitates the process of condensation The formation of water droplets leads to the formation of clouds.
5: List any three human activities that you think would lead to air pollution.
Answer: The following three human activities would lead to air pollution:
(i) Burning of fossil fuels such as coal and petroleum
(ii) industrialization
(iii) Deforestation
Natural resources questions and answers pdf |
Page 194
1: Why do organisms need water?
Answer: Organisms need water for the following reasons:
(i) All cellular processes need water as a medium. Usually, the reactions that take place in our body or within the cells occur between substances that are dissolved in water.
(ii) Since most of the substances are transported in a dissolved form, water is necessary.
2: What is the major source of fresh water in the city/town/village where you live?
Answer: River is a major source of fresh water.
3: Do you know of any activity which may be polluting this water source?
Answer: The discharge of waste water from homes, industries, hospitals, etc. into the river pollutes this fresh water source.
Natural Resources Class 9 Science Chapter 14 notes PDF for free
Page 196
1: How is soil formed?
Answer: Soil is formed by breaking down of rocks at or near the surface of the Earth through various physical, chemical, and biological processes by various factors such as the sun, water, wind and living organisms.
2: What is soil erosion?
Answer: The blowing away or washing away of land surface by wind or water is known as soil erosion.
3: What are the methods of preventing or reducing soil erosion?
Answer: The methods of preventing or reducing soil erosion are:
i.Prevention of deforestation
ii.Plantation of trees
Class 9 General science chapter 14 Natural resources answers pdf
PAGE NO 201
1. What are the different states in which water is found during the water cycle?
Answer: During the water cycle, water is found in solid state (snow, ice, etc.), liquid state (ground water, river water, etc.), and gaseous state (water vapours).
2. Name two biologically important compounds that contain both oxygen and nitrogen.
Answer: Two biologically important compounds that contain both oxygen and nitrogen are:
i.Amino acids
ii.Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA)
3.List any three human activities which would lead to an increase in the carbon dioxide content of air.
Answer: i. Burning of fuels in various processes like heating, cooking, transportation, and industry.
ii. Human induced forest fires.
iii.The process of deforestation includes the cutting down of trees. This decreases the uptake of carbon dioxide for photosynthesis. Eventually, the content of carbon dioxide increases.
4. What is the greenhouse effect?
Answer: Some gases like carbon dioxide, methane, nitro us oxide prevent the escape of heat from the Earth’s surface by trapping it. This increases the average temperature of the Earth. This is called the greenhouse effect. An increase in the content of such gases would lead to a situation of global warming.
5. What are the two forms of oxygen found in the atmosphere.
Answer: The two forms of oxygen found in the atmosphere are: e Diatomic molecular form with chemical formula 02. e Triatomic molecular form with chemical formula O3 known as ozone.
Class 9 General science chapter 14 Natural resources answers pdf | Natural resources questions and answers pdf |
EXERCISES
1: Why is the atmosphere essential for life?
Answer: The atmosphere is essential for life because it maintains an appropriate climate far the sustenance of life by carrying out the following activities:
(i) Atmosphere keeps the average temperature of the Earth fairly constant during day time.
(ii) It prevents a sudden increase in temperature during day tme.
(iii) It also slows down the escape of heat from the surface of the Earth into outer space during night time.
2: Why is water essential for life?
Answer: Water is essential for life because of the following reasons:
(i) Most biological reactions occur when substances are dissolved in water. Thus, all cellular processes need water as a medium to take place.
(ii) Transportation of biological substances needs water as a medium.
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 dependent on soil for a living. Plants obtain water and minerals through the sotl and prepare their food. Other living organisms that live in water are entirely not totally independent of soil because the microbes growing on the soil in water are the primary producers. Primary producers are the main and chief element of the food chain. Various microbes found in soil help in the decomposition of dead plants and animals in water which helps in returning the nutrients and elements back to the water.
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 studied as the collection of various elements like high and low temperatures, humidity, rainfall, wind speed and more using various figures and facts with relevant instruments. Hence on the data collected by the meteorologists, we are able to forecast the weather.
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: Yes. Isolating human activities to specific areas would help in reducing levels of pollution. For example, setting up of industries in isolated regions will control pollution to some extent. The pollution caused by these industries will not contaminate water resources, agriculture land, fertile land, etc.
6. Write a note on how forests influence the quality of our air, soil and water resources.
Answer: Forests influence the quality of our air, sol, and water resources in various ways. Some of them are:
(i) Forests balance the percentages of carbon dioxide and oxygen in the atmosphere. The increasing amount of carbon dioxide caused by human activities is balanced by a larger intake of carbon dioxide by plants during the process of photosynthesis. Simultaneously, a large amount of oxygen is released.
(ii) Forests prevent soil erosion. Roots of plants bind the soil tightly in a way that the surface of the soil cannot be eroded away by wind, water, etc.
(iii) Forests help in the replenishment of water resources. During the process of transpiration, a huge amount of water vapour goes into the air and condenses to form clouds. These clouds cause rainfall that recharge water bodies.
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