The uncontrolled variables are the variables that I cannot control throughout my experiment. Such as the room temperature, I have to keep the apple at room temperature but that may differs as I cannot control the room temp properly but I can try by closing all windows and doors throughout my experiment.
Preliminary Method
- Set out all equipment needed for experiment such as test tubes and test tube racks to hold your solutions, any equipment used to transfer the solutions from one place to another.
- Using a knife cut an apple up into chunks on a cutting tile and make sure all skin and bruised bits are discarded so it just apple flesh you are using as this will effect your results.
- Turn on Bunsen burner and close the whole so the flame goes blue, and place the apple chunks into the saucepan that I stood on the tripod.
- While the apple is cooking, place all six test tubes in the metal test tube rack.
- Fill the first one with 8 ml of water and label it 0%.
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Label the rest 25%, 50%, 75%, 100% and a 6th test tube to a percent of your choice, which was 40%.
- Fill each test tube with the right amount of water and enzyme, shown in the table below.
Figure 2: enzyme concentration volumes
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And a 6th test tube would have a percentage of your choice e.g.
- Once you have done this, the apple will be ready and make sure there are no lumps etc so it’s like applesauce.
- Measure out 35.0 grams exactly on the scale in a beaker.
- Place this beaker in a water bath filled with hot water at about 35 degrees and place the first test tube that is labelled 0% into a another test tube rack in a another water bath.
- While the apple sauce and the solution in the first test tube are heating up, fold a piece of funnel paper so it is creased well and place it in the funnel that is clamped to a clamp stand.
- Put some distilled water onto the filter paper to stick it to the edge of the funnel.
- Place a beaker underneath to catch the water until it has stopped dripping.
- When the temperature of the solution and apple are the same, take 2 ml of the solution out of the test tube and place it into the applesauce with a 5 ml pipette.
- Stir a few times to mix it up. And then pour it into the funnel and after 30 seconds start recording how much juice has dripped through the funnel, let it drip into a 10 ml measuring cylinder and record the volume every 30 seconds for 5 minutes and record it in a results table.
- Afterwards just empty your funnel and wash it out with distilled water and the same with the measuring cylinder underneath.
- Do this method for each test tube twice or three times, you need to do repeats to get an average overall result and so you can see a range of results and work with them to get a more accurate result at the end, and record your results.
I am doing this preliminary experiment very vaguely to get an idea of what will happen, what equipment may be better to use etc, therefore my result s in the real experiment will be more accurate.
Results of the preliminary experiment
Figure 3: preliminary results
This shows the increase of enzyme concentration, increases the rate at which juice is produced; this supports my prediction as the enzyme speeds up the reaction in this experiment, therefore I have predicted that my proper experiment will do the same.
Apparatus
Ideal Method
- Using a small, sharp knife cut up 4 large apples into medium chunks making sure to get rid of all skin and any bruised parts on a cutting tile, because if you don’t then this could affect your results you get at the end.
- When the apples are ready and cut up place them in a saucepan and heat it over a Bunsen burner on as tripod until there are no lumps left.
- Keep stirring with a wooden spoon.
- Meanwhile set up your clamp stand and clap, and clamp the funnel until in a firm hold.
- Place eleven test tubes into your metal test tube rack and fill one of them with 8 ml of distilled water.
- Each test tube will have 8 ml of solution of enzyme in them. But they will have different volumes of enzyme and water. Label each test tube with a separate label as followed: 0%, 10%, 25%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100%.
- The table below shows what each test tube should have in it.
- Now measure the volume of distilled water of the test tube labelled 0%, which will be 8 ml, with a 5 ml pipette, and empty it into the test tube.
- Do the same for each test tube and make sure you measure the distilled water accurately using a graduated pipette.
- Once all the test tubes are filled with the right volume of water, fill them all with the correct volume of enzyme solution, if the enzyme sits at the bottom of the test tube, below the water, take the solution up with the pipette and let it out again, just so it mixes up.
- Once all the test tubes have the correct volume of solution in them, 8 ml, check the apples, they should now look like applesauce. Place a beaker on the scales and turn the scales on. Then measure out 35.0 grams exactly of applesauce into the beaker, this is so you have the exact amount of apple pulp in each filter you do.
- Fill two water baths up with warm water but hot enough to warm up the apple pulp but not too hot as to denature the enzyme.
- Place the plastic test tube rack into one of the water baths and place all the test tubes in the rack.
- Careful to keep and eye on the temperature with a thermometer in each test tube, not letting them go over 40%.
- While these are in the water bath the applesauce should be heating up in a separate water bath and place a thermometer in there to get it to the same temperature as the enzyme solution.
- Meanwhile fold up a piece of filter paper so it has lots of creases so it fits into the funnel.
- Wet the filter paper with some distilled water so it sticks to the side and catch the excess water than drips out of the end of the funnel into a spare beaker.
- Once you’re sure all the excess water is gone, remove the beaker underneath and replace it with a 10 ml measuring cylinder.
- By now the applesauce and enzyme should be up to the maximum temperature, 37 degrees Celsius, take you 5 ml pipette and take up 2 ml of the first test tubes enzyme solution and put it into the 35.0 grams of apple sauce, stir gently a few time with a glass stirring rod.
- Now start the stopwatch. Now using a plastic spoon pour out the applesauce and enzyme solution into the funnel making sure you use the spoon to get every last drop out into the funnel. You have 30 seconds to do this in.
- After the first 30 seconds measure the volume of apple juice in the measuring cylinder below and record it on your result table sheet. And record the volume of applesauce in the measuring cylinder every 30 seconds for 5 minutes and record each measurement on your results table.
- After 5 minutes take the filter with the applesauce in it and put it in the bin.
- Wash the funnel and stirring rod with distilled water and place the funnel back in the clamp stand and repeat this whole process for each concentration.
I have done this ideal method like this so I would have the most accurate results and have a better graph to analyse therefore I could get a better idea of the answer to my question to whether or not the enzyme pectinase increases the amount of juice produced when added to apple.
Method that I used
- The apple was already prepared for us in this experiment so there was no need for the preparation of the apple.
- Set up clamp stand and clamp with the funnel clamped tightly.
- Place all six test tubes in the metal test tube rack.
- Fill the first one with 8 ml of water and label it 0%.
-
Label the rest 25%, 50%, 75%, 100% and a 6th test tube to a percent of your choice.
- Fill each test tube with the right amount of water and enzyme, shown in the table below.
-
And a 6th test tube would have a percentage of your choice e.g.
- Measure out 35.0 grams of applesauce exactly in a glass beaker.
- Place this beaker in a water bath full of warm water and get it up to a temperature of 37 degrees.
- And fill another water bath up of warm water to the same temperature and place the test tube rack in the water bath the test tubes in it and get them up to the same temp as the applesauce, 37 degrees.
- Meanwhile fold up a piece of filter paper so it has lots of creases so it fits into the funnel.
- Wet the filter paper with some distilled water so it sticks to the side and catch the excess water than drips out of the end of the funnel into a spare beaker.
- Once you’re sure all the excess water is gone, remove the beaker underneath and replace it with a 10 ml measuring cylinder.
- By now the applesauce and enzyme should be up to the maximum temperature, 37 degrees Celsius, take you 5 ml pipette and take up 2 ml of the first test tubes enzyme solution and put it into the 35.0 grams of apple sauce, stir gently a few time with a glass stirring rod.
- Now start the stopwatch. Now using a plastic spoon pour out the applesauce and enzyme solution into the funnel making sure you use the spoon to get every last drop out into the funnel. You have 30 seconds to do this in.
- After the first 30 seconds measure the volume of apple juice in the measuring cylinder below and record it on your result table sheet. And record the volume of applesauce in the measuring cylinder every 30 seconds for 5 minutes and record each measurement on your results table.
- After 5 minutes take the filter with the applesauce in it and put it in the bin.
- Wash the funnel and stirring rod with distilled water and place the funnel back in the clamp stand.
- Repeat each step for the rest of the concentrations and record your results in your results table and draw a graph to show you results.
I have used this method as the equipment I could use restricted me, and I felt it was the best way of finding out the answer to my question. I also didn’t do all the percentages that were written down in the ideal method because of time and money, although this would have been better and more accurate for my results.
Processing data
Finding the gradient of a straight line is a simple process, but finding the gradient of a curve is more difficult. I used the tangent method to work out the gradients identified in my results. The tangents were drawn to the full width of the graph (300 sec) in order to give the best accuracy. The gradient of the tangent to the line of ‘best fit’ is calculated by using the formula;
Increase in the X-axis value
Increase in the Y-axis value
In each case the increase in the Y-axis is 300 seconds. The increase in the X-axis is the difference between the points where the tangent intersects the Y-axis and where it intersects the 300-second line at the other end of the graph.
The information in the table below is plotted on a graph to show the processed data of all my results. I chose to do my rate of reaction graph at 150 seconds as graph number 1, which shows all my results, shows that the reactions level out and seem to stabilise at that point.
My results show that the enzyme was able to react more and speed up the reaction of juice producing therefore the higher the concentration of enzyme, the more juice produced.
Result Analysis and Evaluation
When I recorded my results on my results table during the experiment I could only see roughly where I may have had anomalies in my results, but after drawing out my first graph showing an average result of the progress of reaction over 5 minutes, I was able to see where the experiment had not worked out the way it should have and where my anomalies were. Looking at graph number one I can see that all of my of enzyme concentrations had one or two anomalous results, One result was further away from the norm but nothing major.
I felt that after drawing out this first graph that something had gone wrong with the 50% concentration of enzyme because it doesn’t stabilise like the rest of the concentrations as it crosses over the line of best fit of 25% which means that something may have effected my result in that concentration. This could have been due to the uncontrolled variable and the fact that I couldn’t contain it or keep it from affecting my results, I don’t think this could have happened, as the rest of my results seem to be fine, therefore I have come to the conclusion that the 50% concentration of enzyme went wrong because of something that happened during the experiment. It could be the fact that whilst adding the enzyme to the apple, both substances had cooled down too much due to the temperature in the room which may have decreased during the experiment due to a window or door being open, to give more accurate results as the others as they may have been warmer than the 50%. So the temperature of the substances could have caused my result of 50% to go out of sync with the others. But there could be other possibilities, such as time or misreading of volume etc.
Graph two, shows the rate of reaction of the percentage of concentration of enzyme at 150 seconds. I chose to do this because everything seemed to be stabilised by that time on all the concentrations.
It shows that the rate of reaction increases but drops slightly towards the 50% concentration and then increases again. Although this could be simply because my 50% came out different compared the other concentrations, therefore has distorted my graph and made it look as though the rate of reaction doesn’t increase throughout but drops slightly during the increase in enzyme.
I don’t think this is the case as my other concentrations were all increasing at roughly the same rate. The fact that the other concentrations increased at roughly the same rate supports my prediction; the enzyme will increase the amount of juice produced as the concentration of enzyme is increased. I still agree with my prediction and wouldn’t change my mind as I think my results have shown that this is true except for the single one anomalous result throughout my experiment.
Conclusion
I conclude that my experiment has proved that the increase in the enzyme pectinase does increase the volume of juice produced. If I were to do this experiment again, I would make sure I controlled all variables that are listed at the beginning of my coursework after my introduction and plan. This would help accuracy of my results, as there would be less to affect the experiment. I would also increase the number of different concentrations, which would make the results far more accurate as I would have a bigger range to work with and get a better set of results to conclude, as per my ideal method. This would give me a more accurate picture of what is happening with the volume of juice produced and I would be able to state that it does increase the volume of juice produced with a bit more confidence and reassurance as my results would obviously be more accurate and I would be able to state more about what happened to any anomalies that occurred.
Overall I think that my experiment went really well because my results weren’t effected in any way as far as I can see, and I have a good set of result to analyse . I was able to read my results and see the anomalies that occurred and was able to answer my question. Although I would have liked a bit more time to do a slightly bigger range of concentrations to get results that were more accurate.
Results Table
Graph 1
Graph 2
