Chapter 14 Natural Resources

Class 9 Science Chapter 14
Natural Resources NCERT Solutions

Page 193

1. How is our atmosphere different from the atmospheres on Venus and Mars?

Earth’s atmosphere	Venus and mars atmosphere
It is a mixture of nitrogen, oxygen, carbon dioxide and small amount of other gases.	It mainly consist of carbon dioxide.
Life is possible in earth’s atmosphere.	Life is not possible on Mars and Venus atmosphere.

2. How does the atmosphere act as a blanket?

The atmosphere act as a blanket by performing the following function:

1) It keeps the average temperature of the earth fairly constant during day time.

2) It prevents sudden increase in temperature during day time.

3) It slows down the escape of heat into outer space during night.

3. What causes winds?

An uneven heating of Earth’s atmosphere causes winds. During day time, air becomes lighter and rises up. As a result, a region of low pressure is created. To compensate this, air from high pressure region moves to a low pressure region causing wind.

4. How are clouds formed?

During day time, on being heated, a large amount of water evaporates from various water bodies and goes into the air. 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.

The human activities which cause air pollution are:

1) Burning of fossil fuels emit such as coal and petroleum

2) Smoke from factories

3) Deforestation

Page 194

1. Why do organisms need water?

Organism need water because

1) Transportation of substances within the body take place by water.

2) All cellular processes need water as a medium.

3) It helps to maintain body temperature.

2. What is the major source of fresh water in the city/town/village where you live?

River water

3. Do you know of any activity which may be polluting this water source?

The activities which pollute this water source are discharge of waste from residential and commercial area.

Page 196 

1 How is soil formed?

Soil is formed as:

1)Weathering of soil: Breaking of bigger rocks into fine smaller mineral particles. This is done in 3 ways:
1)Physical
2)Chemical
3)Biological

Physical (Sun, water, wind etc.)

Sun: It heats up rocks during the day so that they expand. At night these rocks cool down and contract. Since all parts of rock do not expand and contract at same rate, this result in the formation of cracks and ultimately the huge rock breaks up into smaller pieces.

Water: It could get into the cracks in the rocks formed due to the uneven heating by the sun. If this water later freezes, it would cause cracks to widen.

Flowing water wears away even hard rock over long period of time. Fast flowing water often carries big and small particles of rock downstream. These rocks rub against other rocks and resultant abrasion causes the rocks to wear down into smaller particles. The water then takes these particles along with it and deposit it further down its path.

Wind: Strong wind also erode rocks down. The wind also carries sand from one place to the other.

Chemical 
It involves a variety of chemical processes such as hydrolysis, hydration, oxidation, reduction.
It involves breaking down of complex compounds by carbonic acid present in water and by acidic substances derived from decomposition process of organic matter in soil.

Biological
Lichens, mosses and other plants live on rocks and produce acids, which accelerate the process of rock weathering.

2 What is soil erosion? What are the three methods of preventing soil erosion?

The washing away of top fertile layer of soil by natural agents is called soil erosion.

The methods of preventing soil erosion are:

1) Afforestation i.e. plantation of more and more trees

2) Prevent excessive grazing

3) Build retaining walls

Page 201

1. What are the different states in which water is found during the water cycle?

Water is found in all the three states in water cycle:

Solid state(Snow, ice)

Liquid state(water in lakes, river, underground, ponds , sea etc.)

Gaseous state (water vapour)

2. Name two biologically important compounds that contain both oxygen and nitrogen.

The two biologically important compounds that contain both oxygen and nitrogen are:

1) Amino acids

2) DNA and RNA

3. List any three human activities which would lead to an increase in the carbon dioxide content of air.

The human activities which lead to increase in carbon dioxide content in air are:

1) Burning of fossil fuels

2) Deforestation

3) Industralisation

4. What is the greenhouse effect? 

Certain gases such as Carbon dioxide , Nitrous oxide , methane prevent the escape of heat from the Earth’s surface by trapping it. This increases the average temperature of the Earth. This is called green house effect.

5. What are the two forms of oxygen found in the atmosphere?

The two forms of oxygen found in atmosphere are :

1) Diatomic form ( O₂)

2) Triatomic form (O₃) in ozone

Exercise Page 201, 202

1. Why is the atmosphere essential for life?

The atmosphere is essential for us because it provides an appropriate climate for the existence of life and carrying out various activities by keeping the average temperature of the Earth fairly constant during day time, preventing a sudden increase in temperature during day time, slowing down the escape of heat from the Earth into outer space during night time.

2. Why is water essential for life?

Water is essential for life because of the following reasons:

1) Transportation of substances within the body take place by water.

2) All cellular processes need water as a medium.

3) It helps to maintain body temperature.

3. How are living organisms dependent on the soil? Are organisms that live in water totally independent of soil as a resource?

All living organism are dependent on soil directly or indirectly. Plants need soil for getting support as well as nutrients to prepare their food. Organism depend on plants for food and other substances. Herbivores, depend directly on plants and carnivores depend on animals , which in turn depend on plants. Organism that live in water depend indirectly on aquatic plants which depend on soil for their nutrients.

Question 4. You have seen weather reports on television and in newspapers. How do you think we are able to predict the weather? 

The meteorological department of the government collects data on the elements of weather such as maximum and minimum temperature, humidity, rainfall , wind speed etc. They are able to study these elements using various instruments. The maximum and minimum temperature is measured by thermometer known as maximum-minimum thermometer. Rainfall is measured by a instrument called rain gauge. Wind speed is measured by anemometers. Humidity is measured by  various instruments.

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?

Yes by isolating some activities to specific and limited areas would help in reducing pollution.For ex: Setting up industries in isolated regions will control pollution,  

6. Write a note on how forests influence the quality of our air, soil and water resources. 

Forest balance the concentration of carbon dioxide and oxygen in the atmosphere. The increasing amount of carbon dioxide caused by human activities is balanced by larger intake of carbon dioxide by plants during the process of photosynthesis.

Forest prevent soil erosion. Roots of the plant hold the soil tightly so that the surface of soil cannot be eroded by wind, water.

Forest help in replenishment of water resources. During the process of transpiration, a huge amount of water vapours goes into the air and condenses to form clouds. These clouds causes rainfall which refill water bodies.