Planning b

1.5% hydrogen peroxide

beef catalase solution (freshly prepared)

soap

test tube brush & paper towels

tap water

test tubes of identical height and diameter

test tube rack

beakers

10 ml graduated cylinders

droppers

metric ruler

stopwatch

1. Obtain all needed materials and wash them with soap and brush, rinse with clean tap water and dry with paper towel.

2. Obtain approximately 20 ml of freshly prepared catalase solution and place in a labelled beaker. Use tape to label a dropper as "catalase" for transferring catalase during the experiment.

3. Obtain approximatgely 20 mil of 1.5% hydrogen peroxide solution and place in a labelled beaker. Use tape to label a dropper as "catalase" for transferring catalase during the experiment.

4. Obtain approximately 20 ml of tap water and place in a labelled beaker. Use tape to label a dropper as "catalase" for transferring catalase during the experiment.

5. Because the concentrations of both catalase and hydrogen peroxide differ from day to day, test different mixtures together to determine which combination of catalase and 100% peroxide yields a reaction that comes to within 2 cm of the top of the test tube. These numbers will be used to determine the amounts of catalase and peroxide used below. This action also provides practice for timing and measuring.

6. Using the graduated cylinder, measure 1 ml of catalase and pour into a clean, dry test tube. Carefully add 1 drop of soap to this tube to help hold any oxygen foam produced together. Be sure to insert the dropper far down the tube and avoid getting the drop on the test tube wall.

7. Use Table 1 below to prepare the 100 % peroxide solution in a clean, dry test tube.

8. Have a metric ruler and stop watch handy. One person should time and another should be ready to measure foam height in millimeters.

9. Pour the 100% peroxide into the catalase solution, starting the stop watch as the peroxide hits the catalase. Swirl the test tube once.

10. Finish timing when the foam reaches its highest point. Record time data in seconds in a data table.

11. As the foam reaches its maximum height, use a marker or finger nail to mark the high point. Immediately measure the foam production from the bottom of the foam to the top of the foam (or mark). Record height in millimeters in data table.

12. The 100% hydrogen peroxide concentration, when added to the catalase/soap mixture, is the positive control and shows what the maximum reaction should look like. If lower concentrations show a significantly higher rate of reaction, this means something has happened and the data and or design may be suspect!

13. Repeat steps 6-11 four more times for a total of 5 trials at 100% concentration.

14. Wash all used test tubes with soap and brush and then rinse with water. Dry interior of test tube with paper towel to avoid accidental adjustment of the concentrations of your next tests. Wash droppers and graduated cylinder, especially if there is any hint of contamination.

15. Repeat steps 6-14 for each of the sets of trials at 80%, 60%, 40%, 20% and 0% peroxide. Use Table 1 below to determine the contents of the different peroxide concentrations.

16. Negative Control: Test tubes of 0% peroxide (all water) should be tested with the same amount of catalase and soap tested above. If a reaction occurs, this indicates a problem with procedure or cleanliness. Additional test tubes of 100% catalase can be tested with soap and 1 ml of water as a second negative control. Again, no reaction should occur with this test. Both of these negative tests also should indicate no reaction between soap and peroxide, soap and catalase, water and peroxide, and water and catalase.

17. If additional time allows at the end of the experiment, either repeat any tests at concentrations having suspect data, or continue testing other concentrations, like 90% peroxide, 70% peroxide, etc.

18. At experiments end, return unused and "clean" portions of catalase and peroxide to containers recommended by the teacher. Remove tape from any equipment. Clean all glassware with soap and test tube brush and rinse with clean tap water. Place glassware in test tube racks to dry, and return all equipment to the proper location.

19. Before leaving, wash the lab table and have team mates each wash their hands with soap and water to avoid bacterial contamination (from spilt catalase).