Composition of Air

Composition of Air –

Air is composite mixture i.e. it contains number of different gases with different percentage. Nitrogen, oxygen, carbon dioxide and many

useful gases in present in air.

With the help of below diagram we study gases percentage in air.

So as per above diagrammatic information we know about different gases with their existence in air.

Nitrogen is about 78%

Oxygen is about 21%

Carbon dioxide is about 1% and other gases is also present in small percentage

Let’s study those Gases in brief


Nitrogen is inert gas.

Inert gas never react any other gases.

Nitrogen is colourless gas in appearance; Nitrogen never helps in burning,

Nitrogen gas is as much as important in breathing of human being but plants can use nitrogen gas. It will help them in growth.

High percentage of nitrogen gas can be harmful for human beings.

Question 1) State the uses of Nitrogen.

Answer Nitrogen is used to make a fertilizer.

Nitrogen gas is helps to make dyes.

Used in Pharmacy Industry.

Used in Refrigerant.

Question 2) How nitrogen helps in food preservation process?

Answer- In packed food, nitrogen gas filled against oxygen gas because it is non reacted gas so it saves food and do not react with it.

It also prevents food from bacterial growth.


Oxygen is essential for breathing which we can take from plants.

Oxygen is same like other gases colourless, odorless and tasteless gas.

Oxygen gas in soluble in water also this is the reason aquatic animals can survive in water.

They don’t need to take oxygen from air. It already available in dissolved form.

Oxygen gas is useful gas for burning. If this gas is enter in fire then it will help to grow rapidly. Nowadays oxygen can store in apparatus like oxygen cylinders is available in hospitals.

Those patients are unable to take oxygen from air and suffering from cardiac or asthma like diseases, in this situation stored oxygen gas is used.

Oxygen in must important for living earth if it stops only for few minutes it gives us dangerous results.

Oxygen gas support burning of fire. Lets’ look on one activity that proves oxygen is responsible for burning


Take a candle, transparent jar, and matchbox.

Step 1- Take that candle and fixed on proper surface after this step you should ignite the candle first

Step 2- take transparent jar and cover that burning candle carefully.

Observe for few minutes what you will see.

Question 1) what you will see in step 1?

Answer- candle is continuously heating because it takes favorable oxygen from surrounding air. It melts due to burning.

Question 2) what you will observe in step 2?

Answer- when transparent jar is covered candle, then it starts to flick. Because of insufficient oxygen gas present in jar. Due to this candle stops burning slowly.

Question 3) what you will conclude from this activity?

Answer- when candle is open it easily burn with the help of oxygen which is present in air but after it gets covered by jar then candle have limited oxygen source which is slowly used by candle. All present oxygen gas is used so there is no supporter to help in burning for candle so it gets flick and after that is stop burning.

This is how the oxygen is helps in burning.

Fact of oxygen – if we plant the one acre trees then they can produce oxygen that 18 people can survive in one year. That one acre tree absorbs approximately 2 tons of carbon dioxide.

Questions 1) state the uses of oxygen.

Answer Basically it is essential for life, breathing.

Helps in burning

It is also used in manufacturing of things in industry

Used in medical industry

Question 2) why mountain climber uses oxygen cylinders with them?

Answer- As you reach to high point of mountain there is no favorable air level is present, so oxygen is present in little amount so it is difficult to survive. Therefore climbers use oxygen cylinders.

Fact of oxygen – if we plant the one acre trees then they can produce oxygen that 18 people can survive in one year. That one acre tree absorbs approximately 2 tons of carbon dioxide.

Question 3) Give few examples where oxygen cylinders commonly used.

Answer In laboratory zone (if needed),

Mountain climbing,

In deep water level,

Hospitals ICU.

Question 4) what is combustion?

Answer- A burning process with the help of air is called as combustion.

It can perform with the help of oxygen gas.

Carbon dioxide

Plants use carbon dioxide from surrounding and making their food.

For the process of photosynthesis carbon dioxide is used as raw material. When living things take oxygen from atmosphere it get utilize and when respiration Perform carbon dioxide is produced.

If level of carbon dioxide is increases rapidly in our surrounding we feel suffocated.

Carbon dioxide used in fire extinguisher

Let’s take another activity which proves carbon dioxide is used as fire extinguisher.

Take candle, match box, transparent glass, washing soda (as Base agent) and vinegar (as Acid agent)

  • Step 1- Put some washing soda in transparent glass jar.
  • Step 2- after this step fixed the candle in transparent glass jar carefully.
  • Step 3- Burn that candle with the help of matchbox.
  • Step 4- take some vinegar and add drop by drop on washing soda.

After this step 4 candle is automatically light off. How it’s happen?

Washing soda and vinegar shows opposite property of each other.

When vinegar is added in washing soda it gets react and start rising bubbles and fumes from this. That fumes is none other than carbon dioxide gas. As soon as carbon dioxide as is evolved candle start to flick because carbon dioxide stops burning.

With the help of strong fumes of carbon dioxide gas candle light off automatically.

Therefore, carbon dioxide is used as fire extinguisher.

That is the reason carbon dioxide cylinders can compulsory available in vehicles, offices, hospitals, temples, school or any public place. Because if we face any emergency of fire situation we can use this and stops fire as soon as possible.

Water vapour

Due to evaporation, hot fumes of water are rises. But if they are comes in contact of cooling things or stuck by any surface then that hot vapours is converted is liquid small-small water droplets this process is called as condensation process.

Liquid water is evaporated due to sunlight. Water vapour is rises in high amount and moving to sky direction. In the sky, it makes a condense form called as clouds which can gives us rain.

Question 1) Name the process by which water vapour is formed from water.

Answer- Evaporation.

Question 2) name that process which clouds causes rains.

Answer- Condensation.

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