“My hypothesis is that the higher the substrate concentration the higher the collision rate with substrate enzyme particles, so the faster the substrate would be used up.”
I believe this because of the collision theory, which states that the higher the concentration, means the higher the amount of particles, if there is a higher number of particles then there is a larger chance for the reaction to occur because there is a higher chance of two particles colliding with each other and having a “successful collision”, which means a reaction occurring. Meaning a larger chance for the 0² bubbles being produced as a product of the reaction.
Preliminary Work
I am going to investigate if the PH or temperature changes during experimental reaction. This is called a preliminary experiment. The experiment also will test what volume of catalase and hydrogen-peroxide to use. I will use the following items in the experiment:-
-
Ruler
- Stop Clock
- Test Tube rack
- Test tubes
- Potato discs
- H²O²
This experiment would show me which volume of hydrogen peroxide (Substrate) to use, it would show which suitable substrate to use by measuring the height of the froth. This would see the rate of reaction and the bubbles of oxygen in one minute in the froth.
For the experiment, the volume of reactants (catalase and hydrogen-peroxide) worked however, the reaction was a bit too slow. So I have decided to time how long for 5 cm³ of gas to be collected and not 10cm³.
The temperature and PH are unchanged by the reaction so they would not have to be controlled. I will repeat each experiment twice to make sure my results are accurate as possible. The safety precautions I have placed are that I will wear safety glasses and lab coat (spits from reaction), and clear a radius of metre on the worktop area so there is no accidents of knocking down any items by accident.
Method
Apparatus
- A ruler
- Stop clock
- Water cylinder
- Test Tube Rack
- Test Tubes
- Gas Syringe
- Potato Discs
- H²O²
- Clamp stand
Instructions For Carrying Out The Experiment
- Set up the apparatus as shown.
- Use different concentrations of Hydrogen Peroxide, 10cm³, 8cm³, 6cm³, 4cm³, 2cm³, 0cm³, measure and add into test-tube.(So I would need to do 6 experiments with different Conc.)
- Then add no water to the 10cm³. But when you do experiment with 8cm³ add 2cm³ of water to make the volume the same as equal to 10cm³. And the same for the other concentrations.
- The drop in the 2cm³ of catalase to the solution.
- When you drop catalase, start stop-clock instantly.
- Observe ruler and test-tube, and when the solution creates 5cm³ of gas stop the clock and record your data for the 6 experiments in a table which looks like this :-
My Results and Evidence
I carried out the investigation safely and accurately cleaning out every beaker I use more then once, and I kept it a fair test by not changing the volume of catalase. I collected enough evidence and recorded the experiment and making sure I repeated it.
These are the results I recorded from the experiment:-
I do not need to repeat my investigation as I can clearly tell that the results are somehow similar in that they go down in values, I did the experiment making sure the temperature stays the same and the volume of catalase and none of the other variables change as I have done all these molars on the same day.
To make the results more accurate I will work out the rate for each %, first making sure I average the 2 results. Rate = 1/T x 1000
Analysing and considering the evidence
I think that the evidence that I have collected I will need to present it in a line graph with a line of best fit, this will help me to observe and evaluate and easily compare my investigation. I have found out in my investigation that as the % of pure H²O² (cm³) increases the rate of reaction increases.
I Have made the graph using Microsoft Excel, the following graph is my results (rates):-
Observing my results and my graphs, it shows that my prediction was correct. The reaction does happen quicker when the concentration of the H²O² increases, but the rate at which It is going it starts to get steadier and steadier and looking at the graph you can prove this by working out the gradient the first 20 seconds, is 1.5, and the last 40 seconds of the experiment the gradient is 2, meaning the rate increased by times 2. I believe this is because of the concentration being increased, meaning more particles to collide with and successful collision rate increasing, so rate of reaction increasing more and more as the experiment continues along.
According to my hypothesis which states that, “the higher the substrate concentration the higher the collision rate with substrate enzyme particles, so the faster the substrate would be used up.”, my hypothesis is correct however I have not mentioned (which I have noticed from the actual experiment), that as the reaction goes on, the rate at which it is reacting would increase more and more (as shown before, through explanation of gradient).
As shown in the following table, rate is most at 100%, and least at 20%, proving my explanation as before.
Evaluation
The results obtained were reliable and showed a positive trend in the reaction however the repetition of the experiment showed very different results as shown on the graphs. This can affect the averaged result as it won’t be reliable.
I believe the rate measured were very accurate as they show a trend going upwards as shown in the graph, and there was no anomalies in the time to calculate the rate, as all the rate is going up until it hits a part where the reaction starts to increase faster and faster because of the collision theory of concentration, as I’ve explained previously.
After completing the experiment, I believe that my experiment well, however my results when I did them twice they were not similar and were quite far from each other, even though the apparatus were cleaned and I didn’t change any other variables besides the concentration. To sort out this problem, I would:
1). Have repeated the reaction more times.
2). And used more range of values so I can see the experiment more accurately from a bigger range.
Now I will be doing further work to see how my experiment would be like if I were to change the variable of TEMPERATURE instead of CONCENTRATION. To do this I will keep concentration the same and change the temperature of the substrate through a range of values and keep the enzyme also the same.
From doing this further work, it is very useful to determine a different view of carrying out this experiment, seeing if it would show better results and a different total analysis for the reaction of substrate and enzyme. My range of values are 40°c, 50°c, 60°c, 70°c, 80°c, 90°c, 100°c. I have chosen these range of values because the room temperature of the lab is about 30°c, so to make it easier for us to heat up, to 40°c, and then finally to 100°c, using a Bunsen burner.
The following shows how my plan would look if I were to do a different experiment, changing temperature instead of concentration:-
Method
Apparatus
- A ruler
- Stop clock
- Water cylinder
- Test Tube Rack
- Test Tubes
- Gas Syringe
- Potato Discs
- H²O²
- Clamp stand
- Bunsen Burner, Heatproof mat and Tripod, Thermometer.
Instructions For Carrying Out The Experiment
- Set up the apparatus as shown.
- Setup a separate layout, of Bunsen burner, tripod and heatproof mat, measuring different temperatures, and measuring with a thermometer.
-
Use different temperatures of Hydrogen Peroxide, 40°c, 50°c, 60°c, 70°c, 80°c, 90°c, measure out the same concentration and add into test-tube.(So I would need to do 6 experiments with each with different temps.)
- Then add no water to the 10cm³. But when you do experiment with 8cm³ add 2cm³ of water to make the volume the same as equal to 10cm³. And the same for the other temperatures.
- The drop in the 2cm³ of catalase to the solution.
- When you drop catalase, start stop-clock instantly.
- Observe ruler and test-tube, and when the solution creates 5cm³ of gas stop the clock and record your data for the 6 experiments in a table which looks like this :-
