NCERT Solutions Class 9 Science Chapter 14 Natural Resources

Class IX  Science

Chapter 14 – Natural Resources

Question 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%.

Question 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 time 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.

Question 3: What causes winds?
Answer: An uneven heating of the Earth’s surface causes winds. On being heated, air 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.

Question 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.

Question 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

Chapter 14 – Natural Resources

Question 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.

Question 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.

Question 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.

Chapter 14 – Natural Resources

Question 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.
(i) Sun: During day time, the rocks are heated. This causes the rocks to expand. During night time, these rocks cool down and contract. Since all parts of the rock do not undergo
expansion and contraction at the same rate, this causes the formation of cracks in these rocks. These cracks lead to the breaking up of huge rocks into smaller pieces.
(ii) Water: Water catalyses the process of formation of soil in two ways.
(a) Water goes into the cracks and crevices formed in the rocks. When this water freezes, its volume increases. As a result, the size of the cracks also increases. This helps in the weathering of rocks.
(b) Running water wears away hard rocks over long periods of time. Water moving in fast speed carries big and small particles of rock downstream. These rocks rub against each other, resulting in breaking down of rocks. These smaller particles are carried away by running water and deposited down its path.
(iii) Wind: Strong winds carry away rocks, which causes rubbing of rocks. This results in the breaking down of rocks into smaller and smaller particles.
(iv) Living organisms: Some living organisms like lichens help in the formation of soil. Lichens also grow on rocks. During their growth, lichens release certain substances, which cause the rock surface to powder down forming a thin layer of soil. On this thin layer of soil, some small plants like moss also grow. They further cause the breaking down of the rock particles.

Question 2: What is soil erosion?
Answer: The blowing away or washing away of land surface by wind or water is known as soil erosion.

Question 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

Chapter 14 – Natural Resources

Question 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).

Question 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)

Question 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.

Question 4: What is the greenhouse effect?
Answer: Some gases like carbon dioxide, methane, nitrous 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 green house effect. An increase in the content of such gases would lead to a situation of global warming.

Question 5: What are the two forms of oxygen found in the atmosphere?
Answer: The two forms of oxygen found in the atmosphere are:
(i) Diatomic molecular form with chemical formula O2.
(ii) Triatomic molecular form with chemical formula O3 known as ozone.

Chapter 14 – Natural Resources

Question 1: Why is the atmosphere essential for life?
Answer: The atmosphere is essential for life because it maintains an appropriate climate for 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 time.
(iii) It also slows down the escape of heat from the surface of the Earth into outer space during night time.

Question 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.

Question 3: How are living organisms dependent on the soil? Are organisms that live in water totally independent of soil as a resource?
Answer: Almost all living organisms are dependent on soil. Some depend directly, while some depend indirectly. Plants need soil for getting support as well as nutrients to prepare their food. On the other hand, organisms depend on plants for food and other substances that are essential for life. Herbivores depend directly upon plants, and carnivores depend upon animals, which in turn depend upon plants for food. This makes them depend on soil indirectly. Organisms that live in water are not totally independent of soil as a resource. These organisms depend on aquatic plants for food and other substances. These aquatic plants in turn require minerals for their sustenance. These minerals are carried to water bodies from soil by rivers, rain water, etc. Without the supply of minerals from the soil to the water bodies, it is impossible to imagine aquatic life.

Question 4: You have seen weather reports on television and in newspapers. How do you think we are able to predict the weather?
Answer: The meteorological department of the government collects data on the elements of weather such as maximum and minimum temperatures, maximum and minimum
humidity, rainfall, wind speed, etc. They are able to study these elements using various instruments. The maximum and minimum temperature of a day is measured by a thermometer known as the maximum−minimum thermometer. Rain fall is measured by an instrument known as the rain gauge. Wind speed is measured by anemometers. There are various instruments used to measure humidity. 

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?
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.

Question 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, soil, 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.

 

Question. In which of these cases is the air MOST polluted?
(a) Xanthoria are growing, but NOT parmelia.
(b) Parmelia are growing, but NOT usnea
(c) Pleurococcus are growing, and also usnea
(d) Neither usnea NOR xanthoria are growing

Answer : A

Question. A factory treats its effluents with the aim of making the water completely unpolluted. Which of the following animals should be able to breed there in order for the company to say that the treatment has been a success?
(a) Rat tailed maggots
(b) Bloodworms
(c) Freshwater shrimps
(d) Stone-fly nymphs

Answer : D

Question. Which of these fuels will cause the least amount of Suspended Particulate Matter (SPM) pollution when burned?
(a) Cowdung
(b) Coal
(c) wood
(d) Natural Gas

Answer : D

Question. The Andaman Islands in the Bay of Bengal depend exclusively on rain for their freshwater supply. Some of the hotels in the Andamans started using seawater instead of fresh water for flushing toilets. This is an example of
(a) Recycling of resources
(b) Conservation of resources
(c) Prevention of pollution
(d) Environmental planning.

Answer : B

Question. Here are many reasons why the amount of heat received at higher latitudes is less than the lower latitudes. Which of these is NOT a reason?

 

(a) Sunlight has to pass through a greater thickness of atmosphere in the higher latitudes.
(b) Sunlight has to travel a greater distance to enter the atmosphere in the higher latitudes
(c) Sunlight that strikes the Earth is spread over a greater area in the higher latitudes
(d) More of the sunlight striking Earth is reflected away in the higher latitudes

Answer : B

Question. The figure shows five Roman coins issued between 65 AD and 117 AD. Their names are also shown alongside. From the scale given, we can say that the diameter of the sestertius issued by Nero was about:

(a) 2 cm
(b) 2.6 cm
(c) 3.2 cm
(d) 3.8 cm

Answer : C

Question. Which of these is true about the temperature from the surface of the earth to its core?
(a) The temperature RISES constantly from the surface to the core.
(b) The temperature FALLS constantly from the surface to the core.
(c) The temperature FALLS for about 20 kilometres and then RISES till the core
(d) The temperature RISES for about 20 kilometres and then FALLS till the core.

Answer : A

Question. Study the graphs showing the average temperature (using the scale on the RIGHT) and rainfall statistics (using the scale on the LEFT) for 4 important cities.  The question is based on this data.
A characteristic of cities in the southern hemisphere that can be observed in the above graphs is

(a) They receive most of their rainfall in the summer months
(b) They have summer when the northern hemisphere has winter.
(c) The variation in temperature is quite high across the year.
(d) June is the month of maximum rainfall.

Answer : B

Question. Study this satellite map of India of April 14, 2003. Over which of the FOLLOWING states /  regions are the most clouds observed:

(a) Maharashtra
(b) Karnataka
(c) North-eastern region
(d) Rajasthan

Answer : C

Question. Study the table and answer questions. Which of these is the source for pollutants like lead, NO2 and SO₂ ?

(a) Cars
(b) Wood stoves
(c) Coal-fired power plants
(d) Refineries

Answer : C

Question. Study the table below and answer questions This pollutant is released from cars, causes lung damage and dissolves in water to form an acid. It is

  

(a) Carbon monoxide
(b) Nitrogen Dioxide
(c) Ozone
(d) Sulphur Dioxide

Answer : B

Question. What will happen to the flame when air is blown as shown in the figure?

 

Answer : A

Question. Aditya did the following experiment. He took 2 green bananas in a polythene cover and kept them aside on a shelf. Then he took 2 more green bananas from the same bunch of fruits, and an apple, and put them in an identical polythene cover and kept them on the same shelf.He left both polythene covers undisturbed for two days. What was the hypothesis that Aditya was probably trying to check?
(a) In nature bananas ripen completely in about 2 days
(b) Apples increase the speed at which bananas ripen
(c) Bananas increase the speed at which apples ripen.
(d) Polythene increases the speed at which apples ripen

Answer : B

Question. Since sulphur in the free state is found at depths of more than 150 meters below the Earth's surface, the method of extraction of sulphur differs from other materials. The figure given below depicts this. In this process, super-heated water and compressed air are passed underground through pipes. Due to the pressure, liquid sulphur flows out of the pipe. Which of the properties of sulphur, mentioned in the table above, are used in its extraction?

 

(a) P and Q
(b) R and T
(c) S and W
(d) Q, S and W

Answer : B

Question. A hydrocarbon is burnt in air completely. What are the products obtained?
(a) Carbon dioxide + water
(b) Carbon monoxide + water
(c) Carbon black + water
(d) Graphite + water

Answer : A

 

Question. What is the appropriate name of the sediment that can pass through mesh number 5 BUT cannot pass through mesh number 10?
(a) Small cobble
(b) Coarse gravel
(c) Very fine gravel
(d) Fine sand

Answer : C

Question. The cross section of a lake is shown below. Its surface is frozen. Which of these statements is likely to be MOST accurate about the temperature at the bottom of the lake?

 

(a) It will definitely be 0°C or lower
(b) It will definitely be 4°C or lower
(c) It will definitely be 10°C or lower
(d) It will definitely be 5°C or higher.

Answer : B

Question. What is the MAIN CAUSE of death for fish in water bodies polluted by fertilizers?
(a) decreased nutrition levels for algae
(b) decrease in oxygen levels
(c) increased water temperatures
(d) decrease in number of bacteria

Answer : B