To ensure that the experiment is fairly accurate and I have enough results to show an overall trend, I will use five different concentrations of the substrate, and repeat each experiment three times.
Prediction
I predict that as the concentration of the substrate is increased, the rate of reaction will increase in direct proportion. Therefore, if I were to double the concentration of the substrate, I would expect the rate of reaction to also double. This is because the Collision Theory states that the more particles in a solution, the more likely they are to react, and more quickly. This is because with more particles, there are more collisions, and thus more chance of a successful collision in which the particles react.
An enzyme is a protein that acts as a catalyst. A catalyst is a chemical substance that speeds up a reaction but is not used up during the reaction. One enzyme can be used again and again. There are two types of reactions involving enzymes, anabolic and catabolic. Anabolic reactions are where the enzyme molecule combines two smaller molecules into one larger molecule. Catabolic reactions are the opposite, breaking down a molecule of a substance into two smaller, different molecules. The reaction in this experiment is catabolic, as it is breaking down the hydrogen peroxide into water and oxygen.
The word equation for this is:
catalase
Hydrogen Peroxide Water + Oxygen
The symbol equation is:
catalase
2H2O2 2H2O + O2
Diagram
Step-by-Step Guide
Add 50 cubic centimetres of hydrogen peroxide to a conical flask
Add liquidised celery solution to hydrogen peroxide and place bung over conical flask
After 30 seconds, see how much oxygen has been produced
Celery Concentrations
Results Tables
First Repeat
Second Repeat
Third Repeat
Averages
Analysing evidence and concluding
From the graph I have drawn using the above table of averages, I can see that as the concentration of the enzyme catalase increases, the amount of oxygen produced also increases.
I can also see from my table of results that as the concentration of the enzyme increases, the volume of oxygen increases. This shows that the rate of reaction increases, which supports my prediction.
The reason for this is the Collision Theory, as stated in my prediction. The Collision Theory states that the more particles there are in a solution or area, the higher the rate of reaction will be because there are more particles, therefore there are more collisions, meaning there is an increased chance of successful collisions in which the two particles react.
In this experiment, when the particles react, they break down the hydrogen peroxide and create oxygen and water. As the volume of oxygen increased with positive correlation to the amount of the enzyme in the mixture, I can see that the rate of reaction was increased, thus proving my prediction to be correct.
Please see also attached graph.
Evaluation
The experiment was relatively easy, in that the variables were easy to identify, control or measure, which means that the readings from the experiment should be very accurate. The apparatus was set up in such a way that I think the results are very reliable. The tubing and bung all fitted well into their respective receptacles, thus no oxygen could have escaped from there. The only time and place the oxygen could have escaped was the period between adding the liquidised celery to the hydrogen peroxide, and placing the bung into the conical flask containing the mixture. Unfortunately, there was nothing I could do to stop this, except try and replace the bung as quickly as I could.
There do not seem to be any anomalous results, except in the third repeat when I was using a concentration of forty percent celery. After ten seconds, I measured no oxygen whatsoever, and I presume this was due to a fault in the tubing; perhaps there were slight gaps that I had overlooked during that repeat. However, as this is the only time there is an anomaly within the results, I must assume that the rest of my results are accurate and reliable, and therefore the equipment was set up correctly and performed well.
I think that my results are sufficiently reliable to support my conclusion (see above) because they match my prediction and scientific knowledge of this subject, and the figures I have obtained seem reasonable. I know they are accurate because I was careful to be accurate when taking readings from the gas syringe, and I am sure they are reliable because they do match scientific theory, as taken from text books, etc., and my prediction, which was made using scientific knowledge from various sources.
To improve the reliability of the experiment, I think it would be necessary to find a way of feeding the celery into the conical flask, perhaps via another tube system, where it would be possible to add the celery to the hydrogen peroxide without losing any of the oxygen produced.
