Water trough,
Burette,
Stop clock, Delivery tube,
Clamp stand, Conical flask,
Syringe, Pipette
Glasses/goggles,
PROCEDURE
- I will take the equipment drawn and set it up as shown. *(appendix 2)
- I will fill the burette and water trough with water.
- Using a measuring cylinder, I will put 10ml of Hydrogen Peroxide in the conical flask connected to the delivery tube.
- Trying to prevent water from escaping, I shall turn the burette upside down and clamp it to the stand with the bottom of the burette in the water trough and feed the delivery tube through the burette.
- I will put 0.5ml of Catalase in a syringe and then put it into the conical flask containing the Hydrogen Peroxide.
- As soon as the Catalase is in with the Hydrogen Peroxide, I shall put the bung on and start the stop clock.
- After 30 seconds, I will stop the clock and record how much water has displaced from the burette.
- I shall repeat this with the other concentrations of Hydrogen Peroxide and record the results, as in step 6.
Note – In order for this investigation to be a fair test, I shall repeat each individual concentration of hydrogen peroxide, take the reading and calculate the average of the two readings.
MEASUREMENT RANGE
The measurement range I am going to use for the Hydrogen peroxide is between the concentrations of 0.5% and 3.0%, going up in 0.5’s.
0.5%
1.0%
1.5%
2.0%
2.5%
3.0%
PRELIMINARY WORK
From undergoing some preliminary work I have realized that shaking the conical flask whilst the hydrogen peroxide and Catalase are in it affects the results dramatically. Therefore I have decided to keep the flask perfectly still to get full potential from the results.
SAFETY
Safety is a very important aspect while doing any experiment. In this experiment, in order to keep it reasonably safe I am going to wear safety glasses / goggles at all of the times. I will also be very careful whilst handling Hydrogen Peroxide as it can be a very corrosive substance.
BIBLIOGRAPHY
Biology – A functional approach (M.B.V ROBERTS)
GCSE Biology revision guide – (CGP BOOKS)
www.bbc.co.uk/schools/gcsebitesize/biology/humans\enzymes
Science for GCSE Double award – (GRAHAM HILL)
www.s-cool.co.uk/gcse/biology/enzymes
ANALYSING
TRENDS AND PATTERNS
From the graph (see appendix 3), I can say that as the concentration of Hydrogen Peroxide increases, the volume of oxygen collected gets greater.
Looking at the graph,
Between the concentrations of 1.5% and 3.0%, I can see that when the concentration of Hydrogen Peroxide is doubled, the amount of oxygen collected also roughly doubled.
CONCLUSION
From looking at my graph, I can conclude that as the concentration of hydrogen peroxide increases, the oxygen collected gets greater. Also as the concentration of hydrogen peroxide increases, so does the enzyme activity.
RELATING CONCLUSION TO SCIENTIFIC KNOWLEDGE
From this experiment I have shown that the enzyme Catalase can make a chemical reaction increase, without itself being changed. This is because the rate of oxygen production changed linearly with the increasing concentration of hydrogen peroxide. This shows the amount of Catalase reacting was unchanged and therefore it is not broken down during the reaction.
ORIGINAL PREDICTION
In my plan, I predicted that the higher the concentration of hydrogen peroxide, the greater the amount of oxygen given off.
Was I correct?
Yes, I my original prediction was correct.
EVALUATING
ACCURACY OF PROCEDURE
The accuracy is determined by ensuring that the conditions for the experiment are kept constant. For example, temperature, Ph, and quantity of Catalase w
ere kept constant. It was also important for the concentrations of Hydrogen Peroxide to be accurately measured and freshly prepared.
It was essential to prevent water escaping from the burette to be sure the change in water level was due to the presence of oxygen.
RELIABILITY OF RESULTS
The reliability of the results I collected could be improved by making sure the delivery tube was not kinked as this could block oxygen from entering the burette, which result in the cork popping off the conical flask. I was a bit concerned when between the concentrations of 2.5% and 3.0% the volume of oxygen given off had a range of 30 cm3, whilst between the other concentrations on average the range was about 10 cm3.
PROPOSED IMPROVEMENTS
During the experiment I could improve the following:
- The method of filling the burette with water rather than inverting a full burette I could fill it from the top whilst it was already inverted in the water trough.
- Use higher concentrations ranging from 3.0% to 6.0%. This would enable me to see if the amount of oxygen produced continues to increase when the concentration of hydrogen peroxide increases. I do not believe that this would happen as all the active sites will be used up and the line on the graph will start to curve as the concentrations increase.
- I could also check that the gas given off was definitely oxygen by putting a glowing splint into the burette. In the presence of oxygen it would re light.
I could extend my investigation by including other variables such as changing the Ph or temperature instead of changing the concentrations of Hydrogen Peroxide.