The Effect of Substrate Concentration on the Rate of Reaction

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Method

I generally followed most of my plan for the experiments, but to improve accuracy and reliability, I made one change. In my plan, I said that I was going to use 20cm³ of starch for each experiment. However, in my actual experiment I used 40cm³ of starch. This is because I thought I might not have had enough solution if I only used 20cm³ of starch. If this was the case, then I would have to stop the experiment half way through, which would have prevented me from obtaining accurate results. So for this reason, my results would be more accurate and reliable.

For everything else, I followed my original plan. To ensure the results were accurate, I made sure I accurately measured out the amylase and starch solutions for each experiment. This is because, if I had the wrong amounts, I would not get a valid conclusion, as I will not know whether my results are affected by the concentration of starch, or whether the results I got were due to the amounts of solution used. This would make both my results and conclusion invalid and unreliable. I also made sure that the temperature of the water bath was at the correct temperature and I kept on checking the temperature of both my amylase, and starch using a thermometer. I made sure both solutions were at the same temperature at all times throughout my experiments, so that temperature would not have an effect on my results. This would help me obtain more reliable and accurate results. Also, I made sure that I was drawing the solution up in the pipette beforehand, so that I could put it into the cuvette at exactly 30 seconds. This would make my results more accurate, as the solution would be put into the cuvette at precisely 30 seconds and so time would not have an effect on my results. I also used separate pipettes to measure out the starch, amylase and distilled water so that the solutions don’t mix together before the reaction should start. Also, I repeated each of my experiments two times to make sure I get accurate results. Finally, when I was making up the different concentrations of starch, I made sure that I accurately measured out the distilled water and starch, so that I get the correct concentration of starch.

Results
Below are my results for each concentration of starch, for both the original experiments and the repeats. I obtained my results by putting the cuvettes into a colourimeter and taking a reading for the percentage transmission after every 30 seconds. I used a colourimeter as this would give me numerical values and so my results would be more accurate, because I could not measure the colour intensity accurately by myself, as I can’t put a scale on that. For this reason, the likelihood of human error is minimised. I used a reference point of just iodine solution and distilled water, which was a reading of 100% on the colourimeter.

0.2% starch

Time (secs)% Transmission% Transmission (Repeat 1)% Transmission (Repeat 2)
30111
60111
90302931
120454446
150585759
180706971
210767577
240848385
270908991
3009998100

0.4% starch

Time (secs)% Transmission% Transmission (Repeat 1)% Transmission (Repeat 2)
30111
60111
90111
120111
150182018
180313030
210504951
240565456
270575957
300646563
0.5% starch

Time (secs)% Transmission% Transmission (Repeat 1)% Transmission (Repeat 2)
30111
60111
90444442
120585657
150727171
180787778
210848284
240868787
270898989
300908990
0.6% starch

Time (secs)% Transmission% Transmission (Repeat 1)% Transmission (Repeat 2)
30111
60111
90131513
120434141
150575756
180626563
210716971
240747475
270767778
300787979

0.8% starch

Time (secs)% Transmission% Transmission (Repeat 1)% Transmission (Repeat 2)
30111
60111
90161617
120555454
150707371
180777678
210939293
240949495
270969896
300999999

1% starch...
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