All chemical reactions are affected by temperature. Adding energy to the liquid in the test tube causes the molecules to move faster and faster and this it turn increases the number and frequency of the collisions between them. When molecules collide at high velocity they break apart and the atoms rearrange themselves into different molecules. This is a chemical reaction taking place. Increasing the temperature (which is a measure of the thermal energy in the system), therefore, increases the frequency of the collisions and thus increases the rate at which the product is formed. Most chemical reactions, therefore, produce more product in a unit of time at high temperature than they do at low temperature. In enzyme catalyzed chemical reactions, much the same happens.
However, enzymes are large protein macromolecules, and as the temperature rises the extra energy begins to affect the enzyme molecule itself. This experiment explores the effect of temperature on enzyme activity and also determines the optimum temperature for this enzyme's activity.