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(a) Both assertion and reason are true and the reason is the correct explanation of the assertion

Rain mixed with sulphuric acid is called acid rain

1. Oxygen 

2. Oxides 

3. Acid rain 

4. ammonia 

5. Greenhouse gases 

6. CO₂

7. Nitrogen 

8. refrigerant 

9. rocket fuel 

10. Phosphorous pentaoxide

(a)  Nitrogen

Hydrocarbon + O₂ > CO₂ + Water vapour + Heat energy + Light.

Bacteria converts atmospheric nitrogen directly into soluble nitrogen compounds. 

(b) Carbonates

The process of conversion of iron into its hydrated form of oxide in the presence of air and moisture (humid atmosphere) is called rusting. Rust is hydrated ferric oxide.

4Fe + 3O₂ → 2Fe₂O₃ 

Fe₂O₃ + X H₂O → 2Fe₂O₃ . X H₂O 

(X = Number of water molecules which is variable)

Oxygen reacts with various non – metals like hydrogen, nitrogen, carbon, sulphur, phosphorus etc., to give corresponding non – metallic oxides which are generally acidic in nature.

Non – metal + Oxygen → Non – metallic oxide 

Example: C + O₂ → CO₂

About 78% by volume of air is nitrogen.

Tri oxygen molecule is known as ozone.

1. c 

2. d 

3. a 

4. b

Oxygen is necessary for all acids.

1. c 

2. d 

3. b 

4. a

It is because nitrogen tyres hold pressure longer as  compared to compressed air. Nitrogen gas in the tyre escapes more slowly than compressed air does.

Astronauts wear special protective space suits filled with air when they go to the moon. If they did not wear these space suits, the counter pressure exerted by the body of the astronauts would make the blood vessels burst. The astronauts would bleed.

1. Gills are richly supplied with blood capillaries and can readily absorb the oxygen dissolved in water. 

2. When fishes are taken out of water, the supply of oxygen to the fishes is cut as the fishes cannot absorb and breathe using the oxygen present in the atmosphere. 

3. Hence they die, when it is taken out of water.

CO₂ , N₂O, CH₄ , CFC (Chlorofluorocarbon) etc.

1. Certain gaseous molecules present in the atmosphere absorb the infra red rays and reradiate the heat in all directions. 

2. Hence, these gases maintain the temperature of earth’s surface. 

3. The gases which absorb these radiations are called green house gases and this effect is called green house effect.

1. Potassium oxide (K₂O) 

2. Heating slightly 

3. Au or Pt 

4. Iron Oxide (Fe₃O₄)

1. Solid carbon dioxide, called as dry ice is used as a refrigerant. 

2. The gas is so cold that moisture in the air condenses on it, creating a dense fog which is used in stage shows and movie effects.

When a limited amount of CO₂ is passed through lime water, it turns milky due to the formation of insoluble calcium carbonate. 

Ca(OH)₂ + CO₂ → CaCO₃ + H₂O 

When an excess amount of CO₂ is passed through lime water, it first turns milky and the milkyness disappears due to the formation of soluble calcium hydrogen carbonate, Ca(HCO₃)₂

1. Air exerts pressure. 

2. If there are no holes in the banners and hoardings, they will be damaged. 

3. To make them safe, holes are made to give the air a safe passage.

1. Warm air rises upwards and cool air comes downwards. 

2. To make a stream of cool and fresh air to flow in continuation into the house through the windows, there must be some ventilators in the upper parts of the walls of the house.

Weather is the hour-to-hour,day to day conditions of the atmosphere.

Air pressure is defined as the pressure exerted by the weight of air on the earth's surface.

Air pressure is the pressure exerted by the weight of air on the earth’s surface. As we go up the layers of atmosphere, the pressure falls rapidly.The air pressure is highest at the sea level and decreases with height. Horizonally the distribution of air pressure is influenced by temperature of air at a given place. In areas where temperature is high the air gets heated and rises. This creates a low pressure area. In areas having lower temperature, the air is cold, hence, it is heavy. Heavy air sinks and creates a high pressure area.

(a) The convectional rainfall
(b) The orographic rainfall
(c)The cyclonic rainfall.

In cities we find high rise buildings. The concrete and metals in these buildings and the asaphalt of roads get heated up during the day. This heat is released during the night. Another reason is that the crowded high rise buildings of the cities trap the warm air and thus raise the temperature of the cities.

Wind is the movement of air from high-pressure area to low pressure areas. It is divided into three types:
1. Permanent winds
2. Seasonal winds
3. Local winds
1. Permanent winds. The trade winds, westerlies and easterlies are the permanent winds. These blow constantly throughout the year in a particular direction.
2. Seasonal winds. These winds change their direction in different seasons. For example: monsons in India.
3. Local winds. These winds blow only during a particular period of the day or year in a small area. For example: land and sea breeze. Loo is a local wind which hot and dry and blows in the northern plains of India during summers.

Rainfall is very important for the survival of plants and animals. It brings fresh water to the earth’s surface. If rainfall is less, there is water scarcity which sometimes causes drought like situation. If there is excess rain, floods take place which make the life of the affected people miserable.

Green plants use carbon dioxide to make their food and release oxygen. Humans or animals release carbon dioxide. The amount of carbon dioxide released by humans or animals seems to be equal to the amount used by the plants which make a perfect balance. But this balance is disturbed by burning of fuels, which add billions of tons of carbon dioxide in the atmosphere. As a result, the increased volume of carbon dioxide is affecting the earth’s weather and climate.

Our atmosphere has five different layers. They are:
1. Troposphere: This is the most important layer of the atmosphere with average height of 13 km from the earth. It is in this layer that we find the air that we breathe. Almost all the weather phenomena such as rainfall, fog and hailstorm occur here.
2. Stratosphere: This layer extends up to a height of 50 km. It presents the most ideal conditions for flying aeroplanes. It contains a layer of ozone gas which protects us from the harmful effect of the sunrays.
3. Mesosphere: This layer extends up to the height of 80 km. Meteorites bum up in this layer on entering from the space.
4. Thermosphere: In this layer temperature rises very rapidly with increasing height. Ionosphere is a part of this layer. It extends between 80—400 km. This layer helps in radio transmission. Radio waves transmitted from the earth are reflected back to the earth by this layer.
5. Exosphere: It is the uppermost layer where there is very thin air. Light gases such ashelium and hydrogen float into the space from here.

Nitrogen is essential for the survival of plant. But plants cannot take nitrogen directly from the air. Bacteria, that live in the soil and roots of some plants, take nitrogen from the air and change its form so that plants can use it.

Regions close to the equator get more heat from the sun.

Our atmosphere is composed of mainly two gases—nitrogen (78%) and oxygen (21%). Other gases like carbon dioxide, helium, ozone, orgon and hydrogen are found in lesser quantities. Apart from these gases, tiny dust particles are also present in the air.

A wind is named after the direction from which it blows.

1. Rain
2. Snow
3. Sleet
4. Hail

1. False. When air is moving with cool and soothing is called as breeze.

2. False. Exosphere has low temperature.

3. False. Jan Ingenhousz showed that sunlight is essential to the plant to carry out photosynthesis.

4. True.

5. True.

6. False. The amount of dust in the air is more in windy places then other areas.

A) Uneven heating on the earth

1. – c 

2. – d 

3. – b 

4. – a