Understanding Air Composition and Combustion

The video explains that air is a mixture of gases, primarily oxygen and nitrogen. An experiment is demonstrated where candles are placed under inverted glasses of different sizes to show that oxygen in the air supports combustion. The candle under the smaller glass extinguishes first, indicating less air and oxygen. After combustion, remaining air contains gases like carbon dioxide and nitrogen, which do not support burning. Nitrogen makes up 80% of air, highlighting air's composition as a mixture of several gases.

What is air primarily composed of?

• Only oxygen

• Only nitrogen

• A mixture of gases

• A single gas

In the experiment, why does the candle under the smaller glass extinguish first?

• It has less oxygen available

• The candle is defective

• It has more oxygen available

• The glass is too small

What is the role of oxygen in the experiment with the candles?

• It has no role

• It extinguishes the flame

• It supports combustion

• It prevents combustion

Which gas constitutes the largest portion of air?

• Nitrogen

• Inert gases

• Carbon dioxide

• Oxygen

What percentage of air is made up of nitrogen?

• 100%

• 20%

• 50%

• 80%

Which of the following gases does not support combustion?

• Helium

• Hydrogen

• Carbon dioxide

• Oxygen