Solid carbon dioxide is called dry ice.
Uses:
(i) It is used as a refrigerant
(ii) The gas is so cold that moisture in the air condenses on it, creating a dense fog used in stage shows for movie effects.

The increased green house effect is caused due to increase in the air pollutants and it results in the average increase of temperature of the atmosphere. This is Global warming.

Uses of Nitrogen
(i) Liquid nitrogen is used as a refrigerant.
(ii) It provides an inert atmosphere for conducting certain chemical reactions.
(iii) It is used to prepare ammonia (by Haber's process) which is then converted into fertilizers and nitric acid.
(iv) It is used for inflating tyres of vehicle.
(v) It is used for filling the space above mercury in high temperature thermometer to reduce the evaporation of mercury
(vi) Many explosives such as TNT, nitroglycerin and gun powder contain nitrogen.
(vii) It is used for the preservation of fresh foods, manufacture of stainless steel, reducing fire hazards and as part of the gas in incandescent light bulbs.

Physical properties of Oxygen
(i) Oxygen is a colourless, odorless and tasteless gas
(ii) It is a poor conductor heat and electricity
(iii) Oxygen dissolves readily in cold water
(iv) It is denser than air
(v) It can made into liquid at high pressure and low temperature
(v) It supports combustion.