NCERT Solutions for Class 9th Science
Chapter 14. Natural Resources
Text-book question with solutions:
Q1. How is our atmosphere different from the atmosphere on Venus and Mars?
Ans: Earth's atmosphere is quite different from the atmosphere present on Venus and Mars. The atmosphere of earth consisits of Nitrogen 79%, Oxygen 21% and Carbon dioxide in very less percentage. Venus and Mars, where no life is known to exist, the major component of the atmosphere is found to be carbon dioxide. In fact, carbon dioxide constitutes up to 95-97% of the atmosphere on Venus and Mars.
Q2. How does the atmosphere act as a blanket?
Ans: The air is bad conductor of temperature. It keeps constant the average temperature of the earth during the day and the whole year. It regulates the raising day temperature. Thus the atmosphere act as a blanket.
Q3. What causes winds?
Ans: The uneven heating of the atmosphere in different regions of the Earth like earth's surface and water surface cause winds. On heating up the air creating a low pressure region. The movement of air from high pressure region to low pressure region creates winds.
There are other factors that enfluence these winds:
(i) The rotation of the Earth.
(ii) The presence of mountain ranges in the paths of the wind.
During the day, the direction of the wind would be from the sea to the land.
At night, both land and sea start to cool. Since water cools down slower than the land, the air above water would be warmer than the air above land.
Q4. How are clouds formed?
Ans: 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. Thus vapours condense onto a tiny droplets salt particles called condensation nuclei which form clouds.
Q5. List any three human activities that you think would lead to air pollution.
Ans: Three human activities leading to air pollution are as follows;
(i) Combustion of fossil fuels like coal and petroleum.
(ii) Deforestaion that causes reduction of carbon dioxide utilisation.
(iii) Toxic smoke of industries and colloidal particles of incomplete
combustion of carbon smog and fog.
Q1. Why do organisms need water?
Ans: Organisms need water because;
(i) All cellular processes take place in a water medium.
(ii) All the reactions that take place within our body and within the cells occur between substances that are dissolved in water.
(iii) Substances are also transported from one part of the body to the other in a dissolved form.
(iv) Hence, organisms need to maintain the level of water within their bodies in order to stay alive.
Q2. What is the major source of fresh water in the city/town/village where you live?
Ans: River and ground water.
Q3. Do you know of any activity which may be polluting this water source?
Ans: There are following activities that polluting this water source.
(i) Adding poisonous and harmful chemical substances used by industries.
(ii) Leaving dead and decay body into rivers.
(iii) Human activities like washing clothes, adding home wastes and sewage water etc.
Q1. How is soil formed?
Ans: The rocks at or near the surface of the Earth are broken down by various
physical, chemical and some biological processes. This broken down rocks fine particles forms soil.
Q2. What is soil erosion?
Ans: The upper most layer of soil contains humus and it is quite fertile. It is also lighter. Sometimes soil of this layer carried out by water or wind. The process of removing of soil surfaces is known as soil erosion.
Q3. What are the methods of preventing or reducing soil erosion?
Ans: Deforestation is the main couse of soil erosion, so preventing or reducing this we should encourage the plantaion in very large scale. Because the roots of plants ties soil and it stops the removal of soil surface.
Q1. What are the different states in which water is found during the water cycle?
Ans: The different states in which water is found during the water cycle,
Soild, Liquid and Gas
Q2. Name two biologically important compounds that contain both oxygen and nitrogen.
(i) Amino acids
(ii) Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA)
Q3. List any three human activities which would lead to an increase in the carbon dioxide content of air.
(i) Excessive using/burning fossil fuels in various process like coal, petrolium and industrial uses.
(ii) Release of harmful gases from vehicles.
(iii) Human Induces forest in fire and deforestaion causes decreased uptake of carbon dioxide and releasing of oxygen.
Q4. What is the greenhouse effect?
Ans: Some gases like carbon dioxide, methane, carbon monooxide and nitrous oxide absorb heat present in atmosphere and prevent the escape of heat from the Earth. This heat is trapped by our atmosphere. This is an atmospheric phenomenon. An increase in the percentage of such gases in the atmosphere would cause the average temperatures to increase worldwide and this is called the greenhouse effect.
Q5. What are the two forms of oxygen found in the atmosphere?
Ans: The two forms of oxygen found in atmosphere are as follows;
(i) Diatomic molecular atom with chemical formula O2.
(ii) Triatomic molecular atom with chemical formula O3.