Catalase is an extremely effective catalyst. One molecule of catalase will decompose 40 000 molecules of hydrogen peroxide each second. However, unlike chemical catalyst, which work under a wide range of conditions, enzymes are only able to work under limited conditions.
A catalase is a substrate which alters the rate of a chemical reaction without being used up. The mass of catalyst remains unchanged throughout the reaction. They work at an optimum pH level and they are denatured at high temperatures. It is best for an enzyme to work at pH 6.5 and at 40°c.
A catalyst does not produce any more of the product, but only the same amount at a faster rate. The mass of a catalyst remains unchanged at the end of the reaction. Catalysts are often finely divided powders, pellets and fine gauzes. Catalysts are often transition metals or transition metal compounds.
Possible variables o test: H2O2 and distilled water
Chosen variables to test: H2O2
Fair test: Keep the length of potato and the number of pieces of potato the same. Keep the same concentration of the enzyme. Keep the same temperature, pH and vol. of H2O2 solution. Use distilled water. The total volume must be the same.
Apparatus: 2 measuring cylinders, 1 test tube, 1 potato, 1 test tube holder, 1 core borer, 1 bowl, 1 cooling tube, 1 tile, 1 knife, 1 ruler, 1 test tube rack.
Risk assessment: Make sure at all times you are wearing goggles, gloves, and tuck in ties, tie back hair etc.
Diagram:
Method: collect the apparatus mentioned above. Measure out 20 ml of H2O2 using a measuring cylinder. Pour it into a test tube (make sure test tube is in the test tube rack). Using the borer, bore through the potato. Place the potato on the tile and measure out 5cm of potato. Cut the potato into 5 1cm pieces and make sure there is no skin left on the potato as it will slow down the rate of the reaction. Half full the bowl with tap water. Put the potato in with the H2O2 and quickly set up the apparatus as shown in the diagram. After 5 minutes check how much O2 has been released, this will show how the concentration affects the rate of the reaction as the more O2 in 5 minutes shows that the reaction is working faster. Empty test tube and rinse well. Measure out 16 ml of H2O2 and 4 ml of H2O using a measuring cylinder. Pour it into the test tube (make sure test tube is in the test tube rack). Using the borer, bore through the potato. Place the potato on the tile and measure out 5cm of potato. Cut the potato into 5 1cm pieces. Put the potato in with the H2O2 and H2O and quickly set up the apparatus as shown in the diagram. After 5 minutes check how much O2 has been released. Measure out 12 ml of H2O2 and 8 ml of H2O using a measuring cylinder. Pour it into the test tube (make sure test tube is in the test tube rack). Using the borer, bore through the potato. Place the potato on the tile and measure out 5cm of potato. Cut the potato into 5 1cm pieces. Put the potato in with the H2O2 and H2O and quickly set up the apparatus as shown in the diagram. After 5 minutes check how much O2 has been released. Measure out 8 ml of H2O2 and 12 ml of H2O using a measuring cylinder. Pour it into the test tube (make sure test tube is in the test tube rack). Using the borer, bore through the potato. Place the potato on the tile and measure out 5cm of potato. Cut the potato into 5 1cm pieces. Put the potato in with the H2O2 and H2O and quickly set up the apparatus as shown in the diagram. After 5 minutes check how much O2 has been released. Measure out 4 ml of H2O2 and 16 ml of H2O using a measuring cylinder. Pour it into the test tube (make sure test tube is in the test tube rack). Using the borer, bore through the potato. Place the potato on the tile and measure out 5cm of potato. Cut the potato into 5 1cm pieces. Put the potato in with the H2O2 and H2O and quickly set up the apparatus as shown in the diagram. After 5 minutes check how much O2 has been released.
Changes made after trial run: We doubled the concentration of H2O2 and chopped the potato up into 5 1 cm pieces. We doubled the concentration of H2O2 as with 10 ml you can’t see the reaction as much, it is easier and clearer to get our results from 20 ml of H2O2.
Prediction: I predict that the higher the concentration of H2O2 the rate of the reaction will occur faster, and the more distilled water you add the slower the reaction will occur. I think this because the catalase acts as a catalyst and speeds up the decomposition of hydrogen peroxide
2H202(aq) ⇒ 2H20 + 02(g)
Hydrogen peroxide acts as a biological catalyst, it breaks down the potato/ living cell causing a rapid evolution of Oxygen.