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Term 1 — Chapter 1

Atmosphere

Class 7 - Around the World Geography Solutions


Get Set

Question 1

Read the clues and fill in the blanks. Choose from the box.

greenhouse effect, carbon footprint, stratosphere, global warming, ozone hole
  1. Gradual increase in the average temperature of the earth's surface
  2. Rise in temperature in the atmosphere due to heat trapped by gases
  3. Reduction of the protective layer of ozone in the upper atmosphere
  4. Total set of greenhouse gas emissions caused by an individual
  5. Ozone is found in this layer of the atmosphere

Answer

  1. Global Warming
  2. Greenhouse Effect
  3. Ozone Hole
  4. Carbon Footprint
  5. Stratosphere

Quick Quiz

Question 1

Define atmosphere.

Answer

The envelope of air consisting of a mixture of colourless, odourless and tasteless gases, which surrounds the earth is called atmosphere.

Question 2

............... and ............... are the two main gases found in the atmosphere.

Answer

Nitrogen and Oxygen are the two main gases found in the atmosphere.

Question 3

Name the coldest layer of atmosphere.

Answer

Mesosphere is the coldest layer of atmosphere.

Question 4

The atmosphere keeps the earth's surface warm at night. True or false?

Answer

True.

Question 5

Inside a greenhouse, the air temperature is (less/more) than it is outside.

Answer

Inside a greenhouse, the air temperature is more than it is outside.

Correct the underlined word

Question 1

The underlined word in each sentence is incorrect. Write the correct word.

  1. In the atmosphere, the density of air increases with increase in height.
  2. All weather phenomena occurs in the stratosphere.
  3. A greenhouse is a brick house used to grow plants in cold areas.
  4. A rise in sea level due to global warming will cause flooding of mountainous areas.
  5. Light year is used to measure the thickness of ozone layer.

Answer

  1. In the atmosphere, the density of air decreases with increase in height.
  2. All weather phenomena occurs in the troposphere.
  3. A greenhouse is a glass house used to grow plants in cold areas.
  4. A rise in sea level due to global warming will cause flooding of coastal areas.
  5. Dobson Unit is used to measure the thickness of ozone layer.

Tick the correct answers

Question 1

Which of these gases is found in the lower layers of the atmosphere?

  1. helium
  2. hydrogen
  3. neon
  4. oxygen

Answer

oxygen

Question 2

What is the lower part of the thermosphere called?

  1. troposphere
  2. ionosphere
  3. exosphere
  4. mesosphere

Answer

ionosphere

Question 3

Which of these is a greenhouse gas?

  1. carbon dioxide
  2. oxygen
  3. hydrogen
  4. nitrogen

Answer

carbon dioxide

Question 4

Which of these activities do not produce greenhouse gases?

  1. energy use
  2. agriculture
  3. afforestation
  4. industrial process

Answer

afforestation

Question 5

Which of these gases is responsible for the depletion of the ozone layer?

  1. argon
  2. methane
  3. water vapour
  4. chlorofluorocarbons

Answer

chlorofluorocarbons

Write True or False

Question 1

The composition of air in the atmosphere is uniform.

Answer

False.

Corrected Statement — The composition of air in the atmosphere is not uniform and varies from place to place and from time to time.

Question 2

Helium is found in the exosphere because it is a light gas.

Answer

True.

Question 3

Global warming is caused due to greenhouse gases.

Answer

True.

Question 4

Increase in deforestation is a way to control global warming.

Answer

False.

Corrected Statement — Reduction in deforestation is a way to control global warming.

Question 5

Maximum ozone depletion occurs over the Antarctic region.

Answer

True.

Give reasons for the following

Question 1

The excess accumulation of greenhouse gases disturbs the energy balance in the atmosphere.

Answer

Greenhouse gases are gases which absorb heat energy that comes from the sun and prevents the earth from becoming too cold at night and thus maintain a liveable temperature on the earth. The excess accumulation of greenhouse gases increases the heat and cause rise in air temperature and finally lead to global warming.

Question 2

The depletion of the ozone layer can cause serious damage to different forms of life.

Answer

The ozone layer absorbs the harmful ultraviolet rays of the sun and thus protects life on earth. The depletion of the ozone layer will result in more ultraviolet rays reaching the earth's surface. This can cause serious damage to different forms of life as it can cause skin cancer, eye cataract, immune deficiency and respiratory illness.

Answer these questions

Question 1

What is the atmosphere composed of? Write the names of three impurities found in the atmosphere.

Answer

The atmosphere is composed of gases, water vapour, dust particles and smoke. The gases include nitrogen, oxygen, argon, carbon dioxide, neon, ozone, hydrogen, helium and methane. Nitrogen (78%) and oxygen (21%) are the two main gases while other gases are found in very small quantities. The heavier gases like oxygen, water vapour and dust particles are found in the lower layers of the atmosphere.

Smoke, salts and carbon monoxide are the three impurities found in the atmosphere.

Question 2

Name the different layers of the atmosphere. Write two importance of the atmosphere.

Answer

On the basis of composition, density and temperature, the different layers of the atmosphere are:

  1. Troposphere
  2. Stratosphere
  3. Mesosphere
  4. Thermosphere
  5. Exosphere

Two importance of the atmosphere are:

  1. It maintains the earth's temperature by keeping it warm even at night.
  2. Protection from harmful ultraviolet rays of the sun.

Question 3

Define greenhouse effect and greenhouse gases.

Answer

The earth's atmosphere traps the heat energy that comes from the sun and prevents the earth from becoming too cold at night. This is known as the greenhouse effect. There are gases which absorb the heat energy and maintain a liveable temperature on the earth. Theses gases are called the greenhouse gases. Some of them are carbon dioxide (CO2), nitrous oxide (N2O), chlorofluorocarbons (CFCs), methane (CH4) and water vapour.

Question 4

What is global warming? Write three impacts of global warming.

Answer

The excess accumulation of greenhouse gases in the atmosphere disturbs the energy balance. This can increase the heat and cause rise in air temperature. This increase in air temperature due to excessive concentration of greenhouse gases is called global warming.

Three impacts of global warming are:

  1. Rise in sea level — Increase in air temperature would speed up the melting of glaciers, ice caps and other icebergs in the northern and southern parts of the world which will lead to the rise in sea level and the flooding of coastal areas.
  2. Change in agriculture — Increase in air temperature may affect the world food production as the change in the rainfall pattern would affect crop yields and types of crops cultivated.
  3. Climate change — As the earth heats up, the world climatic pattern will change. Floods, storms, heat waves, fires and droughts could also become more common.

Question 5

What is ozone hole? What was the aim of the Montreal Protocol?

Answer

The vertical column thickness of the ozone layer above 220 DU is considered normal but when thickness of the ozone layer in the stratosphere falls below 220 DU, then it is termed as ozone hole.

The aim of the Montreal Protocol is to phase out the use of ozone-depleting substances and to find or develop non-toxic substances by adopting the following methods:

  1. Safe disposal of air conditioners and old refrigerators at recycling yards.
  2. Avoiding ozone depleting substances from being released into atmosphere.
  3. Properly disposing ozone-depleting substances as environmentally hazardous waste.
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