Catalysts are substances that increase the rate of chemical reactions without undergoing any permanent change in mass or composition. 

These are the most predominant properties of catalysts:

• Alter the rate of a reaction without being consumed in the reaction
• Lower the activation energy of forward and backward reaction as well as threshold energy
• May undergo physical changes during the reaction but their mass and composition remain unchanged at the end of the reaction
• Can be recovered once the reaction is over
• Is easily separable from the products of the chemical reaction
• Are highly specific in action, capable of catalyzing only specific reactions
• Small quantities are sufficient to catalyze a reaction
• Can activate the rate of reaction but cannot initiate reactions
• Does not change the nature of the products obtained through the reaction
• Does not change the energy and extent of reaction
• Does not affect the equilibrium state of the reaction and hence does not change its thermodynamics