Class Nine Science Chapter 14 NCERT Solutions
Chapter 14: Natural Resources INTEXT QUESTIONS (Page No. 193)
Q.1. How is our atmosphere different from the atmospheres on Venus and Mars?
Ans. On Venus and Mars, the major component of the atmosphere is carbon dioxide which constitutes up to 95–97% of the atmosphere. While on earth carbon dioxide constitutes only a small fraction of the atmospheric gases, i.e., it constitutes only 0.03% of atmospheric gases. The main gases on earth are nitrogen (78.08%) and oxygen (20.95%). Presence of oxygen in high concentration makes it easy to breathe for living organisms. This difference in the concentration of oxygen and carbon dioxide differentiates atmosphere on earth from that on Venus and Mars.
Q.2. How does the atmosphere act as a blanket?
Ans. The atmosphere acts as a blanket because:
(i) It keeps the average temperature of the earth constant during the day.
(ii) It prevents a sudden increase in temperature during the daylight hours.
(iii) During the night, it shows down the escape of heat into outer space.
Q.3. What causes winds?
Ans. Uneven heating of the earth’s surface causes wind. Hot air during day time becomes lighter and rises up. As a result, a region of low pressure is created. Then air from a high-pressure region moves to a low-pressure region, causing wind.
Q.4. How are clouds formed?
Ans. When water bodies are heated during the day then a large amount of water evaporates and goes into the air. Some amount of water vapour also gets into the atmosphere because of various biological activities such as transpiration and respiration. The air gets heated and rises up carrying the water vapour with it. The air expands on rising and cools which causes the water vapour in the air to condense in the form of tiny droplets. These water droplets get bigger and from clouds.
Q.5. List any three human activities that you think would lead to air pollution.
Ans. (i) Deforestation i.e., cutting of forests leads to air pollution.
(ii) Burning of fossil fuels like coal, petroleum, etc., leads to air pollution.
(iii) Smoke from industries leads to air pollution.
INTEXT QUESTIONS (Page No. 194)
Q.1. Why do organisms need water?
Ans. Organisms need water to carry out the following activities :
(i) All cellular processes in an organism take place in a water medium.
(ii) Water acts as a universal solvent and helps in transporting substances from one part of the body to another in a dissolved form.
(iii) Water is also required by organisms for many of their activities such as drinking, cooking, transportation etc.
Q.2. What is the major source of fresh water in the city/town/ village where you live?
Ans. Freshwater is present as groundwater and surface water. In our city, we get fresh water from rivers, lakes as well as underground reservoirs made by the engineers.
Q.3. Do you know of any activity which may be polluting this water source?
Ans. Water used for home, hospitals and industrial purposes is discharged into the rivers, lakes, etc., after being used in production processes. The water may contain acid, alkalis, toxic substances, etc. Freshwater bodies are also the sites for the disposal of sewage and other domestic wastes. All these activities pollute the water sources.
INTEXT QUESTIONS (Page No. 196)
Q.1. How is soil formed?
Ans. Soil is formed from parent rock material over millions of years by a process called weathering. In this process, rocks at or near the surface of the earth are broken down into small particles due to physical factors such as sun, wind, rain etc. and it is called physical weathering. The small particles of rocks are then converted into fine particles of soil by the help of plants, animals and micro-organisms, this is called biological weathering.
Q.2. What is soil erosion?
Ans. Soil erosion is washing away of the topsoil with flowing water or wind.
Q.3. What are the methods of preventing or reducing soil erosion?
Ans. Methods of preventing or reducing soil erosion?
(i) It can be prevented by intensive cropping.
(ii) It can be prevented by providing proper, drainage canals around the fields.
(iii) Soil erosion in hilly areas can be prevented by practising terrace farming.
(iv) It can be prevented by planting more and more trees and sowing grasses.
(v) It can be prevented by constructing strong embankments along the river banks.
INTEXT QUESTIONS (Page No. 201)
Q.1. What are the different states in which water is found during the water cycle?
Ans. States are:
(i) Gaseous state: In the form of water vapour which evaporates from the surface water.
(ii) Liquid state: It is formed by the condensation of water vapour and can be seen in the form of rain.
(iii) Solid-state: It is formed by the freezing of liquid droplets in the upper layer of atmosphere which can be seen in the form of snow, hail or sleet.
Q.2. Name two biologically important compounds that contain both oxygen and nitrogen.
Ans. Proteins and nucleic acids (DNA and RNA).
Q.3. List any three human activities which would lead to an increase in the carbon dioxide content of the air.
Ans. The three human activities leading to an increase in the carbon dioxide content of air are:
(i) Burning of fossil fuel, such as petrol, diesel and coal in various activities like transportation and industrial processes.
(ii) Burning of wood and charcoal for heating, cooking etc.
(iii) Deforestation reduces the green plant and tree population and utilisation of atmospheric CO2 during photosynthesis.
Q.4. What is the greenhouse effect?
Ans. The greenhouse effect is an atmospheric phenomenon, in which an increase in the percentage of some gases such as carbon dioxide in the atmosphere causes the average temperature to increases worldwide.
Q.5. What are the two forms of oxygen found in the atmosphere?
Ans. Elemental oxygen is normally found in the form of a diatomic molecule, i.e., (O2): But at the upper layers of the atmosphere, there is another form of oxygen which is a triatomic molecule of oxygen and it is called ozone (O3). Thus, the two forms of oxygen found in the atmosphere are O2 and O3 (ozone).