The retention of heat energy by carbon dioxide and other greenhouse gases like cholorofluorocarbons, methane, water vapour and  oxides of nitrogen, which are present in the atmosphere, is called greenhouse effect.

The solution of sodium bicarbonate is filled in fire extinguishers and it reacts with sulphuric acid to form carbon dioxide.

Automobile emissions can be checked by installing catalytic converter. It converts unburnt hydrocarbons and carbon monoxide gas into harmless water vapour and carbon dioxide.

Burning of candles and and fuels is an example of rapid oxidation.

The unburnt particles released during combustion of fuels are called soot.

Rust is a reddish brown hydrated oxide of iron. It is formed when iron is exposed to oxygen in the presence of moisture.

The percentage of argon in the air is 0.9%.

Manganese dioxide is used as a catalyst in the laboratory preparation of oxygen.

Helium is preferred over hydrogen in hot air balloons because hydrogen can readily catch fire and helium is lighter than any of the other rare gases.

Argon is used in welding metals.

Nitrogen is used as a cooling agent in refrigeration.

The transformation of atmospheric nitrogen into a usable form is known as nitrogen fixation.

Solid carbon dioxide, known as dry ice, sublimes at -56.4^oC.

Acid rain is mostly caused by emissions of sulphur and nitrogen, which is highly acidic in nature. It has harmful effects on plants, aquatic animals, etc.

Cooling down of water vapour in the air higher up in the atmosphere is known as condensation.