This video lecture from Group VA and Group VIA Elements (F.Sc. second year Chemistry) covers the physical properties of nitrogen dioxide. It is a reddish brown gas with a pungent smell which dissolves in water to give a blue acidic solution. The gas attains a solid structure upon cooling which is dinitrogen tetraoxide, essentially a dimer of the molecule in gaseous state. The solid is colorless but upon heating it transitions into pale yellow liquid and later into a reddish brown gas at various temperatures. Further heating results in the decomposition of nitrogen dioxide into nitric oxide and oxygen gas. Find more e-learning material and educational video lectures in Urdu at maktab.pk. These videos are free to use for promotional and commercial purpose by keeping the credits to Maktab.