This video lecture from Reaction Kinetics (F.Sc. first year Chemistry) is an extension of the previous lecture on catalysis. A catalyst is defined as a substance which alters (increases or decreases) the rate of reaction but stays chemically unchanged at the end of reaction. Addition of catalyst to control the rate of reaction is termed as catalysis. This lecture particularly helps in understanding the way catalyst works by decreasing the activation energy which in turn allows for higher number of effective collisions as evident through Maxwell-Boltzman normal distribution. Homogenous and heterogeneous catalysis are defined in terms of phase of catalyst and reactants. Autocatalysis involves a product which serves as a catalyst and the rate is proportional to time. Enzyme catalysis involves complex protein molecules which act as catalysts in biological reactions mostly in living cells. 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.