Give reasons for the following observations:
(a) Air holes of a gas burner have to be adjusted when the vessels heated get blackened by the flame.
(b) Use of synthetic detergents causes pollution of water.
(a) Air holes of a gas burner have to be adjusted because the blackening of the vessel shows that the air holes of the gas stove are getting blocked and hence the fuel is not burning completely due to insufficient supply of oxygen.
(b) Some of the detergents (synthetic) are not bio-degradable, that is they cannot be decomposed by microorganisms like bacteria and hence cause water pollution.