Methods of keeping the control variables controlled:
I will use a water bath to help maintain the desired temperature of hydrogen peroxide. If the thermometer indicates the temperature is decreasing, then I will add more hot water to the water bath in order to sustain the temperature.
In order to keep both the amount of hydrogen peroxide and yeast solution the same, I will be using a 1ml pipette and 10ml of measuring cylinder. This is to make sure that I get the correct measurement of yeast and hydrogen peroxide so that the investigation will be fair.
I will keep the same length of time for each experiment by starting the stopwatch as soon as the yeast solution of dropped into the hydrogen peroxide and as soon as it reached one minute, I will measure the volume of oxygen gas given off.
Independent variable:
Temperature ˚C
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Room temperature- 22 o C
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37 o C
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45 o C
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60 o C
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70 o C
Dependent variable:
Volume of oxygen gas produced (ml)
The materials that I will be using in this investigation are:
- 10ml measuring cylinder
- 1ml pipette
- Boiling tube
- Beaker (water bath)
- Kettle
- Thermometer
- Container
- Stopwatch
- Rubber tube to connect the boiling tube to the measuring cylinder filled with water
Method:
Firstly, I will boil the water using a kettle to get my desired temperatures (22o C, 37 o C, 45 o C, 60 o C, 70 o C).
Then, I will use a 10ml measuring cylinder to measure 10ml of hydrogen peroxide into the boiling tube. Since my investigation involves in the rate of enzymes in different temperature, I will leave the boiling tube containing the hydrogen peroxide and heat it into the water bath (beaker).
I will leave the boiling tube in the water bath for at least 30 seconds until the temperature of the hydrogen peroxide reached to 60 o C.
This step will also be repeated when doing with the other desired temperatures. The temperatures can be measured using a thermometer and the thermometer must be kept constantly into the hydrogen peroxide in order to keep track of the temperature of the hydrogen peroxide and ensure that it does not exceed or decrease from the desired temperature.
Secondly, I will add 1ml of starch using the 1ml pipette (for accuracy) and place it into the boiling tube containing the hydrogen peroxide. I will then quickly cover the boiling tube with a rubber lid and the tube will be placed directly underneath the measuring syringe (upside down measuring cylinder). Due to the shortage of facilities, I will need to use a measuring cylinder filled with water and place it in the container with a rubber tube directly underneath it to measure the volume of gas bubbles given off.
For the next step, I will use a stopwatch to time every minute so that each minute, I will measure the volume of oxygen gas given off from the reaction and record it down. This will be repeated 3 times to get a more valid and reliable data and to spot any anomalies present throughout the experiment.
I will use this step with the other temperatures.
I will then collect the data and write it in a results table.
Volume of oxygen gas produced for each temperature given during the investigation.
The results are written in 2 decimal places. However, there are many errors and uncertainties which effects the result’s validation such as the temperature may have an error of 1o C and the recordings on the measuring cylinder of the gas bubbles given off may have an error of 1ml.
Graph to show the overall trend of vol. of gas given off in different temperatures:
From these set of results, I conclude that the low temperatures such as 22 o C slows down the rate of reaction as the result shows that the reaction between hydrogen peroxide and yeast solution has a slower rate of reacting as there was less of oxygen gas given off. Heat gives energy to the enzymes and helps them to make the reaction faster so the lack of heat makes the enzyme slow down.
However, when the temperature starts to increase, there is a gradual change in the rate of reaction as the oxygen gas bubbles given off increased. The higher the temperature such as the 45 o C, seems to work best than the other given temperatures as it has achieved the highest volume of gas bubbles given off within the time limit.
45 o C is the optimum temperature here as it gave out the highest volume of gas bubbles given off and any temperature above that, the volume of gas bubbles given off started to decrease down the slope. It is an optimum temperature because anything that goes beyond this temperature, the enzyme seemed to be non-functional. I believe this is because it has reach to a certain temperature where the enzyme starts to denature and unravels the chains of amino acids so therefore it loses its ability to catalyze a substrate and this is proven as the investigation shows that there was a dramatic fall of volume of gas bubbles given off after 45 o C.
Therefore, my hypothesis that as the temperature increases, the speed of reaction will also increase. When a temperature passed its optimum temperature, the rate of reaction will also decrease as the enzymes cannot cope with the high rise of temperature and therefore the enzymes will be denatured so there will be no reaction as they can no longer bind to a substrate and act as a catalyst.
The investigation proves my hypothesis as the results came out as predicted.
However, even though that there is a link relating to the results and my hypothesis, I still cannot 100% guarantee that my hypothesis is correct as I need to take the errors and uncertainties into account so I will need to do a further thinking of how to eliminate these errors and improve my investigation.
The measurement materials that I used such as the pipette didn’t really gave me an accurate measurement of 1ml as there is a 0.5ml of uncertainty so I could have used a better accurate measurement such as burette pipette which gives a better measurement than a normal pipette.
The water bath may also not be the best way to maintain temperature constantly as the temperatures can decrease or increase so it will take time to adjust the temperature so better equipment would be an electronic water bath which can maintain the desired temperature constantly.