Answer:
Increasing the temperature of the reaction mixtures increases the average kinetic energy possessed by particles in the reaction mixture aka particles move faster. This increases the frequency of collision between enzymes and substrates particles hence increases the frequency of effective collision in the correct orientation thus increasing rate of enzyme substrate reaction.
However, if the temperatures increases too high, the bonds in the enzymes' structure (hydrogen bonds, hydrophobic interactions) will be disrupted, altering the 3D structural conformation of the active site of the enzyme. Substrates will no longer be able to recognise and bind to the enzyme hence the enzyme can be considered to be denatured, with a loss of function