NCERT Solutions for Class 9 Science Chapter 14 Natural Resources
Chapter Name | NCERT Solutions for Class 9 Science Chapter 14 Natural Resources |
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NCERT Intext Questions
1. How is our atmosphere different from the atmospheres on Venus and Mars?
Solution
Earth’s atmosphere is a mixture of nitrogen (79%), oxygen (20%), and very small fraction of carbon dioxide, water vapours and other gases. Thus, this environment makes the existence of life possible on Earth. However, the atmosphere on Venus and Mars mainly consist of carbon dioxide in large amount, range from 95% to 97%.
2. How does the atmosphere act as a blanket?
Solution
There are some reasons that atmosphere acts as a blanket :
- Temperature of the Earth remains average during day time/whole year.
- Prevents a sudden increase in the temperature during day time.
- Slows down the process of escaping of heat from the surface of the Earth into outer space during night time.
3. What causes winds?
Solution
An uneven heating of the Earth’s surface causes winds. Air becomes lighter and rises up on being heated. As a result, a region of low pressure is created. Then, air from a high pressure region moves to a low pressure region. This is the reason of winds.
4. How are clouds formed?
Solution
A large amount of water evaporates from various water bodies and goes into the air during day time, on being heated. 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 forms water droplets by condensation. The dust and other suspended particles helps in the process of condensation. This formation of water droplets leads to the formation of clouds.
5. List any three human activities that you think would lead to air pollution.
Solution
Three human activities leading to air pollution are :
- Industries smoke,
- Use of transport (burning of fossil fuel)
- Deforestation.
6. Why do organisms need water?
Solution
The organisms need water :
- For different cellular process
- For transportation of substance from one place to another inside the body
7. What is the major source of fresh water in the city/ town/village where you live?
Solution
Rivers.
8. Do you know of any activity which may be polluting this water source?
Solution
The discharge of waste water from homes, industries, hospitals, etc. into the river pollutes this fresh water source.
9. How is soil formed?
Solution
Soil is formed through various physical, chemical, and biological processes by breaking down of rocks at or near the surface of the Earth.
- Sun : The rocks are heated up by solar rays during day. Due to this heat rocks expand. These rocks cool down and contracts during night time and due to this process the rocks break down.
- Water : It helps in breaking of rocks in two ways :
(a) Water goes into the cracks formed in the rocks. The size of cracks increases by freezing the water. This helps in the weathering of rocks.
(b) Water moving in fast speed carries big and small particles of rock downstream. These rocks rub against each other and break down. - Wind : Strong winds carry away rocks, which causes rubbing of rocks. This results in the breaking down of rocks into smaller and smaller particles.
- Living Organism : Some living organisms like lichens help in the formation of soil.
Solution
The blowing away of land surface by wind or water is known as soil erosion.
11. What are the methods of preventing or reducing soil erosion?
Solution
The methods of preventing or reducing soil erosion are :
- Plantation of trees and plants
- Prevention of deforestation
- Prevent excessive grazing
12. What are the different states in which water is found during the water cycle?
Solution
Water is found in three different states during the water cycle :
- Solid (ice)
- Liquid Water (ground water, river water, etc.)
- Gaseous State (steam, water vapour)
13. Name two biologically important compounds that contain both oxygen and nitrogen.
Solution
Two biologically important compounds that contain both oxygen and nitrogen are :
- Amino acids
- Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA)
14. List any three human activities which would lead to an increase in the carbon dioxide content of air.
Solution
Three human activities are :
- Burning of fossil fuels
- Forest fires caused by human activities
- Deforestation includes the cutting down of trees. Thus, consumption of carbon dioxide decreases. Eventually, the content of carbon dioxide increases.
15. What is greenhouse effect?
Solution
Some gases like carbon dioxide, methane traps the heat and prevents the escape of heat from Earth’s surface. This increases the average temperature of the Earth. This is known as greenhouse effect.
16. What are the two forms of oxygen found in the atmosphere?
Solution
The two forms of oxygen found in the atmosphere are :
- Diatomic molecular form with chemical formula O2 .
- Triatomic molecular form with chemical formula O3 known as ozone.
NCERT Exercises Solutions
1. Why is the atmosphere essential for life?
Solution
The atmosphere is essential for life because it maintains an appropriate climate for the sustenance of life by carrying out the following activities :
- Atmosphere keeps the average temperature of the Earth fairly constant during day time.
- Prevents a sudden increase in temperature during day time.
- It also slows down the procedure of escaping heat from Earth’s surface during night time.
2. Why is water essential for life?
Solution
Water is essential for life because of the following reasons : Substances are dissolved in water during biological reactions. Cellular processes need water as a medium to take place. 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?
Solution
Almost all living organisms are directly or indirectly dependent on soil. Plants need nutrients from soil to prepare their food and other organism depend on plants for their food. Only plants make their food but all other organism directly or indirectly depend on plants, which in turn depend upon soil for food. Organisms that live in water depend on aquatic plants for food and other substances. These aquatic plants require minerals for their sustenance. These minerals are carried to water bodies from soil by rivers, rain water, etc. Without the supply of mineral, it is impossible to imagine aquatic life.
4. You have seen weather reports on television and in newspapers. How do you think we are able to predict the weather?
Solution
The meteorological department of the government collects data on weather, such as maximum and minimum temperatures, maximum and minimum humidity, rainfall, wind speed, etc. by using various instruments. Rainfall is measured by an instrument known as the rain-gauge. The maximum and minimum temperature of a day is measured by a thermometer known as the maximum-minimum thermometer. Wind speed is measured by anemometers. There are various instruments used to measure humidity.
5. We know that many human activities, lead to increasing level pollution of air, water-bodies and soil. Do you think that isolating these activities to specific and limited areas would help in reducing pollution?
Solution
Yes, Isolating human activities in particular areas would help in reducing levels of pollution. For example : Setting up of industries in isolated regions will not contaminate water resources, agriculture land, fertile land, etc. It will control pollution to some extent.
6. Write a note on “how forests influence the quality of our air, soil and water resources”.
Solution
Forests influence the quality of our air, soil, and water resources in various ways. Some examples are :
- Balance the percentages of carbon dioxide and oxygen in the atmosphere by photosynthesis process.
- Prevent soil erosion as roots of plants bind the soil tightly.
- Replenishment of water resources during the process of transpiration.