Water (H20) Kettle
Ice Cubes Stop Watch
Measuring Cylinder
Step by Step Method
- Cut a piece of potato measuring 1cm³.
- Measure out 10cm³ of hydrogen peroxide and pour it into the test tube.
- Pour some water into a beaker and also put some ice in to make the temperature decrease.
- Place the test tube filled with hydrogen peroxide into the beaker.
- Put the thermometer into the test tube and measure the temperature. Keep adding ice cubes to the water until the temperature of the hydrogen peroxide is 5ºC. (Place the thermometer into the test tube and not the beaker of water because you are measuring the temperature of the hydrogen peroxide and not the water.)
- Fill the other beaker with water.
- Drop the piece of potato into the test tube and seal it with a rubber bung with the delivery tube attached to it and start the timer.
- Put the other end of the delivery tube into the other beaker of water.
- Count the bubbles as they begin to appear in the beaker of water.
- When the timer indicates that two minutes has gone by: stop counting the bubbles.
In this experiment we are able to work out the enzyme activity because the hydrogen peroxide breaks down the enzymes this is what is produced:
HYDROGEN PEROXIDE WATER + OXYGEN
2H202 2H20 (l) + 02 (g)
When the hydrogen peroxide breaks down the enzymes, water and oxygen is produced. Both the water and oxygen are transported down the delivery tube and are disposed in the beaker of water. It is not visible when the water is disposed but it is visible when the oxygen is disposed because little bubbles form. We count the bubbles to work out the rate of enzyme activity.
Fair Testing
To obtain a valid set of results, it is important that the experiment is conducted fairly. To make this experiment fair: we have to keep a few factors the same.
- Type of Potato – We have to keep the same type of potato because different types of potato. Organic potato may have a different amount of enzymes than normal potato or an old potato may have a different quantity of enzymes compared to a potato. To make this test very accurate: we should use the same potato each time we conduct the experiment.
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The Amount of Hydrogen Peroxide (H202) – We have to keep the amount of hydrogen peroxide the same because the more hydrogen peroxide there is; the more time it would take the enzymes in the potato to break it down into:
HYDROGEN PEROXIDE WATER + OXYGEN
2H202 2H20 (l) + 02 (g)
- The Amount of Potato – We have to keep the amount of potato the same because when the enzymes in the potato are breaking down the Hydrogen peroxide, if there is more potato in a different temperature then there would be more enzymes which means that the Hydrogen Peroxide would be broken down even more. This would then not result in a fair test.
- The Length of the Delivery tube – We need to make sure that the length of the delivery tube (each time we do the experiment) is the same because as time is an important factor in this experiment it may take longer for the gas to travel through a long delivery tube into the beaker of water.
- Time – Time is a very important factor in this experiment. We as a class decided to observe the enzyme activity for two minutes. It is important that we observe the activity for only two minutes each time we conduct the experiment.
Range of results
The results that need to be taken are the amount of bubbles that are produced at the end of the two minutes. I am repeating each experiment three times. This is how I am going to lay my table out:
I will repeat the experiment three times and then I will find out the average amount of bubbles. This will make my evidence more accurate. I may have made a mistake whilst conducting the experiment so by repeating the results three times and finding the average, I am obtaining a more accurate result.
Safety
Safety is a very important factor when conducting experiments. If we don’t pay attention to the safety factors that we need to take into consideration, then someone can get hurt quiet seriously. When we were conducting our experiment all of the participants should make sure that we had our safety goggles on. We should roll up our sleeves and those with long hair should tie them back neatly. We must make sure that we don’t have any loose clothing on us. All the books and any unnecessary items should be cleared from the desk. We should try to avoid chemicals from making physical contact with our skin as it may cause irritation. We should also make sure that we don’t sniff directly up a test tube as it could lead to dangerous side effects. Whilst measuring the temperature of the hydrogen peroxide, we should careful insert the thermometer into the test tube because if we drop it too hard: the test tube might break. This would cause the hydrogen peroxide to leak, which in turn will be considered as an unfair experiment and so the results will not be recorded.
OBTAINING EVIDENCE
Suitable table of results
This is where I recorded all my results whilst conducting the experiment:
This table of results shows the results of my experiment. The first column shows the different temperatures I used to calculate how temperature affects the rate of enzyme activity. The second column shows the results of my first experiment. The third column shows the results of my second experiment. The fourth column shows the results of my third experiment. To get a more accurate result, I found the average of all three of my results and have inserted them into the fourth column of my table.
Repeated results
In this particular experiment I made sure that I repeated the experiment at least three times. I did this to get a more accurate result. If I had only conducted the experiment once, then I would be more liable to have made a mistake. By doing the experiment three times and then finding the average of it, I am more confident that I have produced are more reliable.
ANALYSIS
From the graph I can tell that the temperature does affect the rate of enzyme of enzyme activity but there is an optimum temperature. In this particular experiment the optimum temperature was 35ºC. Enzyme activity takes place best at this point. This can be viewed on the graph as the enzyme activity increases when the temperature is increase but after it reaches an optimum temperature it starts to deiterate.
The results I have got goes to prove that what I predicted before conducting the experiment was right. I predicted that: the higher the temperature the higher the rate of enzyme activity, which would result in a higher number of, bubbles being produced, but the temperature should not get too hot or too cold because the process will slow down again. I predicted that my graph would be:
This is exactly what has happened. The graph of results that I predicted is similar to the graph of results containing the figures I obtained whilst conducting the experiment.
Scientific Explanation
Enzymes are biological catalysts that help to speed up reactions. As the temperature increases, the enzymes gain more energy. This causes more collisions between reactants and enzymes and the rate of the reaction increases (usually the rate doubles for every 10ºC increase in temperature). However, as enzymes are proteins they lose their shape above about 40ºC. They become denatured. They therefore cannot control the reaction above this temperature resulting in the decrease of enzyme activity or none at all. The longer the conductor, the more particles there are in the way and so the harder the electrons find it to flow. In a longer wire there will be more collisions and so the electrons will lose even more energy.
EVALUATION
There were some points in my graph (anomalies), which did not fit and were quite far from the best-fit line. This mainly occurs because I had not plotted the graph in the write place. This also occurred because I had not noted the correct number of bubbles whilst the experiment was taking place. The anomalies were quiet obvious because when the best-fit line was drawn these points were not within the range of the best-fit line.
I think my method was quite efficient and straightforward. It was a clear step-to-step method, which if followed properly would have resulted in a perfect experiment. To improve my method I would give more specific information to make the experiment run as smoothly and as accurately as possible.
During the experiment my accuracy of counting the bubbles was not very precise because all the bubbles were not the same size. It was not fair to count two small bubbles as double the value of one large bubble. Next time I could trap the bubbles in a measuring cylinder and measure the volume of gas to give a more accurate reading. This is turn would make my results more reliable to give a fair conclusion.
I have acquired a strong and good set of results, which could be used to show somebody: how temperature affects the rate of enzyme activity. To support the evidence I have gained even further I think it would be wiser to repeat the results more often whilst conducting the experiment. Equally I could conduct the same experiment several times and then merge all my results together.
