Kemtec®. Students study the action and nature of enzymes as catalysts while performing 5 experiments. Using experimental controls and variables, students observe the action of amylase on starch, invertase on sucrose, and pepsin on protein. Students examine the rate of enzyme-catalyzed reactions and use changes in solution color and pH as indicators of chemical change. As an optional exercise, students can use a spectrophotometer to quantify their results. Materials are sufficient for 24 students working in 6 groups of 4.