I will make my investigation a fair test by repeating it more than once; I will use timings of 20 seconds, and will repeat this for each concentration of substrate 3 times and calculate an average. Another thing I will do to make my investigation a fair test is by using the same amount of enzyme(1 spatula) & substrate(2ml) each time, although changing the concentration of the substrate.(2.5%,5%,10%,15%,20%) I will also keep the amount of water in the measuring cylinder the same, and the concentration of the enzyme.
Equipment
~1 spatula Yeast
~5 different concentrations of hydrogen peroxide
~3 boiling tubes
~Delivery tube & a bung
~Trough
~Measuring cylinder
~Water
~Stopwatch
Preliminary experiment
~Half fill trough with water
~1 spatula of yeast in a boiling tube
~2ml of hydrogen peroxide e.g. a 20% concentration
~Put the bung in the top of the boiling tube after substrate added, with the delivery tube in the upside down measuring cylinder, in the trough.
~I will wait 20 seconds each time, for 3 times with each different concentration of hydrogen peroxide.
Diagram
Preliminary Results
1 spatula yeast
2ml hydrogen peroxide
Changes
Method
Step 1-Fill a trough half full with water
Step 2-Take a 100cm3 measuring cylinder and fill with water to the very top
Step 3-Carefully put your hand n the top of the measuring cylinder & place upside down in the trough so no water can escape, slowly and carefully slide your hand away whilst quickly placing the cylinder so it is stable on the bottom of the trough.
Step 4-Get a boiling tube and measure out 1g of yeast into it, get a clamp stand.
Step 5-Place the boiling tube containing the yeast into the clamp stand so it is just above the water in the trough.
Step 6-Get another test tube or boiling tube and place a 20% concentration of hydrogen peroxide into it. Use the guide on the pipette to measure out 4ml.
Step 7-Get a delivery tube & bung, place the transparent ‘L’ shaped end underneath the lip of the measuring cylinder in the trough, so it is just inside the cylinder.
Step 8-Get a stopwatch. Pour the hydrogen peroxide into the tube with the yeast in it, and then very quickly place the bung securely into the tube. Once the bung is securely in place, start the stopwatch. Once it has reached 10 seconds, take the first reading of how much gas has been produced, do this again when it reaches 20 seconds and take a final reading at 30 seconds.
Step 9-Once you’ve completed this for the 20% concentration, repeat it with concentrations of 15%, 10%, 5%, and 2.5% concentrations. Repeat each concentration, including the 20% 3 times in total.
Results Table
Observations
As soon as gas was being produced, bubbles began to form, at the beginning they started off as quite large bubbles, but once it was past 10 seconds, the bubbles started to shrink.
Interpreting My Data
I have found that the higher the concentration of hydrogen peroxide, the quicker the rate of reaction was. There is a correlation between the two.
My prediction was proved correct.
On my graph, the line of best fit is a curve, this shows that the rate of reaction quickens to collect more gas in 30 seconds with a 20% concentration than at 10 seconds with a 10% concentration. This is a positive correlation. The 5% and 2.5% concentrations results are very close with the amount of gas collected. These are also the anomalous results; these are highlighted on my graph.
Conclusion
My findings were that there is a correlation with the higher the concentration of hydrogen peroxide, the more vigorous and quicker the rate of reaction was e.g. 20% concentration the amount of O2 produced was 63.7 cm3 at 30 seconds on average. This is because there are more enzymes for the substrates to collide with, so more products are released. When the substrate collides with the active site of an enzyme it makes products, in this experiment the product was oxygen gas. Once the product has been released, the active site of the enzyme becomes denatured, and the active site is not the right shape for the enzymes to collide with, this is why towards the 30 second reading, the oxygen produced is not a lot more than the 20 second reading, but the 20 second reading, a lot more gas is produced because the active sites has not yet become denatured. This proved my prediction right. My experiment went very well, although I ended up with anomalous results, it helped me to explain things a bit more.
Evaluating my Investigation
I used goggles to keep my eyes protected throughout the practical stages in my investigation. I used the nearest sink to where I was working to ensure the least amount of spillages was made. My investigation was a success; the results show a positive correlation. My results helped me with my conclusion to sum up how my results proved my prediction was correct. I think my data is quite accurate because I did everything I could to ensure it was a fair test.
I had two anomalous results. For 10 seconds, the 2.5% concentration of hydrogen peroxide collected more gas than the 5% at 10 seconds. This lowers the reliability of my results.
Something that could have affected the results is the equipment. The first delivery tube we used got clogged up so we had to change it, this new tube could have been wider or shorter than the first one. I carried out repeats then took my averages. Another thing that could have affected my results is the people. Something that could have affected the results is the measuring of the yeast and hydrogen peroxide, towards the end of the experiment we were running out of time, and may have taken wrong amounts of yeast and substrate which could be why there are anomalous results.
I feel like my results aren’t as reliable as they could be, if we did the experiment again and had more time I think we would have more reliable results because we wouldn’t have messed up the amounts of yeast and hydrogen peroxide. If there were more concentrations I would be able to explain more about the rates of reaction because if there was a 25% or a 50% concentration I would have a more reliable set of results because I would have repeated it 3 times and had more results to work with.
