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The only correct statement is 

a) In winter the winds flow from the land to the ocean.

Two methods to find out wind direction are: 

1. Using an anemometer. 

2. A simple method is to hold some dust and release in the air. Dust will fly in the direction of wind flow.

a) moving 

b) uneven 

c) hot, cold 

d) high, low

Correct option is A) downwards

1. Take a balloon. Blow air into it. As we fill it up, it expands and it becomes harder to press the walls of the balloon. The inside air exerts pressure on the walls of the balloon. 

2. Open the mouth of the balloon slightly. Air from the balloon comes out. 

3. We can open the mouth less or more and control the flow of air. 

4. The air in the balloon is at high pressure and it goes towards low pressure area. 

5. We already know that when air moves, it is called wind. Air moves from the region where the air pressure is high to the region where the pressure is low.

C) Air expands on heating

Factors like wind speed, wind direction, temperature, and humidity contribute to the development of cyclones.

Tropical cyclones are like giant engines that use warm moist air as fuel.

Wind speed plays an important role in the formation of storms.

Air expands on heating and contracts on cooling.

Correct option is A) Wind speed

D) Air is every where

Anemometer: Instrument for recording wind speed

The moving air is called wind.

It has become easier to study cyclones with the help of advanced technology like satellites and radars.

Correct option is C) Wind

Uneven heating on the earth causes wind movements.

D) heavy wind and rain

Correct option is D) land and sea
 

Correct option is B) June

(i) On a humid day the air is full of water vapour. Hence, evaporation is very slow. This is the reason why wet clothes take longer time to dry on a humid day.
(ii) Insolation comes through vertical rays on equator. Thus, it covers up less space but we feel more heat there when it goes up from equator towards poles, the sun rays become slanting. Needless to say that slanting rays come on the earth covering longer distance. Although these slanting rays heat up more space, the degree of hotness is felt less. This is the reason why amount of insolation decreases from equator towards poles.

During night trees absorb oxygen and release carbon dioxide. Therefore, anyone who sleeps under tree, will not get oxygen, which can cause breathing problems, suffocation etc.

1. In soda bottle carbon dioxide gas is dissolved in water under pressure. 

2. The gas in the bottle expands. 

3. Hence, the pressure inside the bottle increases. 

4. Thus the bottle may burst in hot summer.

Anyone can develop a habit of breathing through their mouth, but certain conditions increase your risk. 

These include:- 

1. Chronic allergies 

2. Hay fever 

3. Chronic or recurring Sinus infections 

4. Asthma 

5. Chronic Stress and Anxiety

1. Oxygen 

2. Oxygen 

3. Oxygen 

4. Dust particles 

5. Carbon-di-oxide

1. If we remove the plants from the aquarium, oxygen percentage will be decreased. So fishes would die.

2. If the aquarium is kept in the dark place, the green plants will not prepare their food due to lack of sunlight and carbon di oxide. So the plants get spoiled.

The roots can absorb oxygen from the small air spaces in soil.

Our earth is surrounded by a huge envelope of air. It is called atmosphere.

1. Air is used by plants and animals for breathing. 

2. Air is used for burning fuels like wood, coal, kerosene, LPG etc. 

3. Compressed air is used to fill tyres of various kinds of vehicles. 

4. Ozone layer, present in the atmosphere, helps in preventing harmful radiations of the sun from reaching the earth’s surface. 

5. Under extra – ordinary conditions such as: 

(a) a patient having breathing difficulties,

(b) a mountaineer climbing a high mountain, 

(c) a diver going deep into the sea, oxygen gas cylinders are used for breathing purposes. 

6. Blowing air is used to turn the blades of wind mills. The wind mills are used to draw water by running pumps, run flour mills and to generate electricity.

The components present in the air with percentage Nitrogen – 78%, Oxygen – 21%, Carbon di oxide, Argon, Water vapour and other gases – 1%.

Our earth is surrounded by a huge envelope of air called the atmosphere. The atmosphere is made of five different layers – the Troposphere, the Stratosphere, the Mesosphere, the Ionosphere and the Exosphere.

The reasons behind fire extinguishers throw a stream of CO, while putting-off fire:-

1. CO₂ is a colourless and in normal concentrations, odourless gas. It doesn’t react with burning materials, so it doesn’t create any toxic or other by products while putting-off fire. 

2. Carbon dioxide doesn’t conduct electricity, making it an ideal fire suppressant for use in the places where a large amount of electricity may be present. 

3. CO₂ acts on fires in two ways: The release of the gas under pressure has a cooling effect, as can be seen by the resulting mist cloud and ice particles; the gas also displaces the oxygen that’s necessary to maintain combustion

Traffic assistants are continually exposed to smoke emitted out from the vehicles. Inhaling the pollutants in the smoke may cause breathing and lung problems. So they wear a mask on duty.

The atmosphere is essential for life because it maintains an appropriate climate for the maintenance of life by carrying out the following activities:

1. The atmosphere keeps the average temperature of the Earth fairly constant during the day time.

2. It prevents a sudden increase in temperature during the day time. 

3. It also slows down the escape of heat from the surface of the Earth into outer space during the night time.

Pour some lime water in a glass tumbler Bubble some air using a straw through the litne water. After a few minutes, lime water will produce a white precipitate and that the lime water will turn to a milky white solution. This shows the presence of Carbon- di-oxide in air.

Correct answer is (c) Oxygen

Respiration in plants:

During respiration, plants take in oxygen and release carbon-di-oxide, just as animal also do. Gaseous exchange with air in atmosphere takes place in plants with stomata.

Photosynthesis: 

During photosynthesis, carbon-di-oxide from the air and water from the soil react in the presence of sunlight to produce food. Plants release oxygen during photosynthesis which is much more than the oxygen consumed by the plants during respiration.

Respiration in animats:

When we breath in air, the oxygen present in the air reacts chemically with digested food within the body to produce carbon-di-oxide gas. The inhaled air contains more oxygen while the exhaled air contains more carbon-di-oxide.

So plants sent out more oxygen during the photosynthesis. Animals sent out more carbondi-oxide during respiration. Plants take carbondi-oxide for photosynthesis. Animals take oxygen during respiration. So plants and animals maintain the balance of oxygen and carbon-dioxide in air.

(d) keeps the food fresh

Correct answer is (c) Oxygen

Correct answer is (a) 78%

Correct answer is (b) 16%

Argon gas at low pressure is used for filling electric bulbs.

The percentage of oxygen in air by volume varies from 20.8% to 20.9%.

The main components of air are:

1. nitrogen

2. oxygen

3. carbon dioxide

4. water vapor

5. inert or noble gases

(a) Respiration : Respiration is a chemical process that takes place in all living beings (slow in plants). In this process, oxygen present in inhaled air reacts with the digested food material in the body. This results in release of energy, carbon-dioxide and water. 

Sugar + Oxygen → CO₂ + Water + Energy. 

(b) Photosynthesis : Process of producing food by green plants taking CO₂ from air, water from soil by roots and in presence of sun light and chlorophyll is called photosynthesis. 

(c) Combustion : Combustion also called burning “is burning of substance in oxygen of air completely producing heat and light is called combustion.”

The natural way of adding oxygen to air which involves green plants is called photosynthesis.

1. False. 

Correct: Atmospheric nitrogen cannot be directly absorbed by the plants to form plant proteins.

2. True

3. False. 

Correct: Oxygen is a gaseous non-metal essential for respiration.

4. True

5. True

The ancient belief about the nature of matter was that it is compound of four elements

1. fire

2. air

3. wood

4. earth