Investigate the effect of changing the substrate concentration on the rate of reaction of hydrogen peroxide in the presence of catalase enzyme

I also know this from my preliminary work on the same experiment which showed that the reaction did take longer with diluted Hydrogen Peroxide.

Variables

I will use Hydrogen Peroxide as my independent variable by changing the volume of

H2O2 5 times to make the test more accurate. I will use the following percentages of concentration: 20% 40% 60% 80% 100%. I will dilute the H2O2 with distilled water. This is because tap water contains ions such as chloride which could alter the results and make them unreliable.

The time taken for the enzyme to reach the surface of the H2O2 will be my dependent variable. I will use a stopwatch to record the time it takes for the enzyme to reach the surface. The stopwatch will begin when the enzyme touches the surface of the H2O2 in the test tube. It will stop when it re-touches the surface.

The controlled variables will include the following:

• Temperature
• Ph
• Volume
• Concentration
• Bead size

To control temperature I will heat the test tubes in a thermostatic water Bath at 50ْْْ . The Ph will remain the same throughout the experiment. The concentration of enzyme will be controlled by placing in a known volume of enzyme and not diluting it. I will draw up 5ml of the mixture used to make beads for each bead to make them the same size.

Apparatus

100ml Calcium Chloride 1.4%

100ml of 0.05g Catalase

10ml 0f 2% Sodium Alginate

5ml Glycerol

1 litre 20 volume Hydrogen Peroxide

5 Test tubes

5 drops Borax Carmine

100ml Distilled Water for dilution

Stopwatch

Chinagraph Pencil

Goggles

Glass rods

Beaker for mixing

Spatula

Measuring Cylinders (10ml)

Teat Pipettes

A small Beaker

5 test tube rack

1 water bath set at 50ْْْ

I have chosen to use a stopwatch because it’s a lot more reliable than looking at a clock or watch as it gives you the semi seconds as well and also it always you to focus on the bead moving from the surface to the bottom and back, unlike with a watch or clock were you would have to look at the time and not the bead.

The Chinagraph Pencil is so that you do not confuse the test tubes and get inaccurate results. Measuring cylinders are needed to measure accurate quantities of the above liquids.

Method

1. Place a mixture of sodium alginate and glycerol in a small beaker.
2. Add to the mixture 10ml of catalase solution and 3 drops of carmine Borax
3. Stir the mixture with the glass rod for 5 minutes
4. To make the beads draw up some of the mixture from the beaker into a plastic pipette.
5. The beads must be of the same size.
6.  Bigger sized beads will make products faster than smaller sized beads making the test unfair. Therefore the beads must be of the same size
7. Squeeze the mixture into the beaker of calcium chloride solution.
8. Repeat the bead making process until you have 20 beads
9. If the beads float in the beaker, do not use them in the experiment because it will make the results unreliable and if some float and some do not the test will become unfair.
10. Place same sized test tubes into test tube racks
11. Place volumes of Hydrogen Peroxide into the test tubes.
12. The hydrogen should be of different volumes as shown in the table below
13. Make sure you have labelled each test tube with the volume of Hydrogen Peroxide it contains using the chinagraph pencil

14. Make a table to record your results in such as the above table
15. Using a spatula take one bead from the beaker of Calcium Chloride
16. Drop the bead into test tube 1
17. Once the bead has touched the surface of the hydrogen peroxide, start your stopwatch.
18. Do this for each experiment to make it fair.
19. Make sure you are recording the time taken for each bead to touch the surface at the same time for each bead.
20. As soon as it touches the surface again stop the stopwatch.
21. Repeat 3 times and record results.
22. Use the closest two results to work out the average time taken. This will make your results more accurate.
23. To work out the average for the closest two results you use the following equation:         result 1 + result 2 ÷ 2 = average result
24. Repeat the steps 15 to 23 for the remaining test tubes.

Risk Assessment

1. Hydrogen Peroxide is considered to be a mutagen and so must be handled with care.
2. Do not touch it with your hands
3. It’s a corrosive chemical and can cause irritation to eyes and skin.
4. Goggles must be worn at all times.
5. Breathing hydrogen peroxide can cause irritation to the nose and throat.
6. Avoid inhaling it at all times.
7. Further breathing of it cause irritation to the lungs and result in coughing and shortness of breath
8. Do not deliberately inhale substance  
9. Further exposure can result in a build up of fluid in the lungs which would require immediate medical attention
10. Do not eat any bead or drink any liquids
11. Wash hands thoroughly after experiment.
12. Wipe any spills with a paper towel.