Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Air is a mixture of several gases, water vapour, and dust particles.
Nitrogen () is the most abundant gas in the atmosphere, making up approximately of the air. It does not support burning.
Oxygen () makes up about of the air. It is essential for the survival of all living organisms and is required for the process of burning (combustion).
Carbon dioxide () makes up a very small component (about to ) of the air. Plants use for photosynthesis and release .
Water vapour () is present in varying amounts depending on the weather and location. Its presence is crucial for the water cycle.
Dust and smoke are also present in the air. The amount of dust varies from place to place and time to time.
The balance of oxygen and carbon dioxide in the atmosphere is maintained through photosynthesis by plants and respiration by plants and animals.
📐Formulae
💡Examples
Problem 1:
Calculate the approximate volume of Oxygen () present in of air.
Solution:
Volume of Oxygen = .
Explanation:
Since Oxygen () constitutes of the air, we multiply the total volume of air by to find the volume of oxygen.
Problem 2:
Why does a candle burning in a closed jar extinguish after some time?
Solution:
The candle extinguishes because the Oxygen () inside the jar is consumed during the process of combustion.
Explanation:
Burning requires Oxygen (). In a closed jar, the supply of is limited. Once all the is converted into Carbon Dioxide () and other byproducts, the flame can no longer be sustained.
Problem 3:
How is the presence of water vapour () in air demonstrated?
Solution:
By placing ice-cold water in a glass; droplets of water appear on the outer surface of the glass.
Explanation:
When air comes in contact with a cool surface, the water vapour () present in it condenses into liquid water droplets. This proves that air contains moisture.