Properties of Air and its Composition

1) How Do Helium Balloons Float?

• Helium is a gas that is less dense than air.
• When a balloon is filled with helium gas, it floats in the air displacing the air molecules.

2) What Are Inert Gases?

• The gases that do not react with anything under a given set of conditions are called inert gases.
• Examples of inert gases are helium, neon, xenon, and argon.
• These gases are used in chemical factories to reduce the chances of chemical hazards caused by highly reactive substances.

3) Write Some Uses of Carbon Dioxide.

• Carbon dioxide is used as a fire extinguisher.
• Carbonated beverages have carbon dioxide gas.
• Plants use it during photosynthesis.
• It is necessary for the greenhouse effect, which is essential to maintain the earth's temperature.

4) Why Are Freshly Fallen Meteorites Too Hot To Touch?

• Meteorites are celestial bodies that fall on the earth’s surface during a meteor shower.
• When meteorites travel through the atmosphere, a frictional force is exerted by air.
• Most meteorites burn entirely due to the heat generated by the frictional force of the air.
• Therefore, the meteorites that reach the earth’s surface remain very hot.

5) How Will You Prove by an Activity That Air Exerts Pressure?

The following activity proves that air exerts pressure—

• Take a hard-boiled egg and remove its shell.
• Light a matchstick and put it carefully into an empty glass bottle.
• Put the peeled egg in the bottle’s mouth, keeping the narrower end of the egg towards the mouth of the bottle.
• After a few minutes, the egg will drop into the empty glass bottle.
• It happens because the flame of the lit match consumes all the air in the bottle, which creates low air pressure. As the air pressure outside is higher, the egg is pushed inside the bottle.

6) What Is Altitude Sickness?

• The uneasiness felt while travelling in mountain areas is called altitude sickness.
• It happens due to reduced oxygen concentration in the air as we move upwards to greater heights.
• As a result, an individual's breathing rate increases, which may sometimes lead to nausea and nose bleeding.
• So, mountaineers carry oxygen cylinders during expeditions.