Diagram
Rubber bung
Gas cylinder
Delivery tube
Oxygen bubbles
Beehive
Test tube
Trough of water
I will use 2ml of hydrogen peroxide and 2ml of yeast decided from preliminary work. A measuring cylinder will measure the two solutions. Before measuring the hydrogen peroxide I will have to dilute it. When this has been done the two solutions will have to be put in a test tube with a delivery tube to react together with a bung on top of the test tube. A bung will be placed on top of the test tube to prevent any escape of gas. A trough of water will be placed beside it. This will contain a beehive with a gas cylinder placed on it with water. The trough of water is used to measure the amount of gas produced from the catalysed reaction. The side arm of the test tube will connect with the beehive and gas cylinder. The gas cylinder will measure any gas that’s been produced. As gas is collected the water inside will decrease indicating that the reaction is taken place. This reaction will be timed for two minutes and after this I will record the amount of gas collected. The evidence I will be planning to obtain is how much gas is produced when different concentrations react with yeast. Different concentrations of hydrogen peroxide will have different amount of gas produced. The equipment I selected is needed to be used accurately as possible so I can obtain accurate evidence. The equipment is relevant for this task.
Fair test
To keep this investigation fair I must only vary the concentration of hydrogen peroxide and keep the factors constant. To do this investigation I must choose one factor to vary and keep the other factors constant, so it will be a fair test. I have decided to vary the hydrogen peroxide concentration. The temperature will remain constant at room temperature (25°C). The pH of the hydrogen peroxide will be constant. The yeast concentration will also have to be constant. Different beakers were used. Different syringes were used. This was done to avoid any mix up.
Safety
While doing this experiment safety precautions must be taken seriously
∗ Plastic gloves were worn as I was handling dangerous chemicals.
∗ Safety coat was worn.
∗ Goggles were worn to protect my eye.
∗ Any coats and bags were put aside.
∗ Carefully handling the equipment as I was using glass.
Here is how I made my dilutions of hydrogen peroxide.
Method
- Collect all the apparatus needed from the apparatus list.
- Set up the experiment as indicated from the diagram.
- Make the dilutions of hydrogen peroxide. (Follow the table on how to make dilutions)
- Measure the amount of hydrogen peroxide to 2ml then put in test tube and put on the bung on top.
- Measure the amount of yeast to 2ml.
- Inject this through the needle at the top of the bung and start the stopwatch at the same time.
- Start to collect gas and wait for two minutes.
- When two minutes is up, then record the reading of the gas cylinder.
- Record the readings in a neat table.
- Do this method each time.
Hypothesis
My prediction I make is that as the concentration increases the amount of gas produced will also increase. As the hydrogen peroxide is reacting with the yeast, gas will be produced. The reason for this is that the yeast will breakdown the hydrogen peroxide to form oxygen gas.
H202 Yeast H202 + 02
If the concentration of the hydrogen peroxide is strong it will contain more particles in its solution. If the concentration is strong the yeast will break it down and gas will be produced. If the concentration of the hydrogen peroxide is weak it will contain less particles in its solution and therefore the amount of gas produced will be less due to less particles of hydrogen and oxygen.
The concentration of a solution is how much and how strong there is in that solution. If the concentration of a solution contains a lot of particles it means that the solution is strong. The yeast only breaks whatever there is. If the solution has a strong concentration it will breakdown a lot of particles in that solution as when a solution has a weak concentration it will breakdown less particles in that solution.
Preliminary Work
Before I start my investigation I must do a trial run to see if I need to make any changes to my plan. I first decided to use 5ml of hydrogen peroxide and yeast to react together. This was a very fast reaction and I was not able to collect any reliable evidence. After this I used 2ml of each solution and it was at a correct rate of reaction. I decided to run the experiment for one minute but it was a short time as the reaction wasn’t near complete. I changed the time to two minutes as this gave better results. From my preliminary work I had a slight problem. When I added the hydrogen peroxide with the yeast to react together in the test tube I quickly put the rubber bung on top. This was not a good idea because as soon as the hydrogen peroxide and yeast are mixed together the reaction starts and oxygen will be produced but it will escape instead of being collected. To over come this problem I decided to leave the bung on top and insert a needle so that no oxygen will be lost.
From my preliminary work I decided to use a range of
1.0, 0.8, 0.6, 0.4 and 0.2 molar
This range of concentration is perfect to collect the evidence needed. I will repeat the experiment five times for each concentration to get a total reading of 25.
Here are my trial run results with the range I have chosen.
Trial run results
Secondary sources
To plan this investigation I had to analyse it in more detail. To achieve this I used secondary sources:
- A book called “Edexcel Modular Science”
- Encyclopaedia
From these resources I obtained relevant information that will help me plan my investigation.
Now I have done my plan I collected the evidence needed including repeats.
Results obtained from Hydrogen peroxide reacting with Yeast
Average results of Hydrogen peroxide reacting with Yeast
From these repeats I have done I calculated the average. Here is an example how I worked out the average.
- Molar
16.0 + 14.0 + 16.5 + 15.5 + 16.0 ÷ 5 = 15.6 Cm3
Analysis
From my evidence I have found out that as the concentration increases the amount of oxygen also increases. From the results I obtained I plotted it on a line graph to analyse the results in great detail. From this I can then draw a line of best fit and also see if there is any trend or pattern. My graph shows that as the concentration of the hydrogen peroxide increases the amount of oxygen also increases. The line of best fit is appropriate because it will show any sort of trend and also show any anomalies. My graph shows a positive correlation with a couple of anomalies. The evidence I have obtained is sufficient to write a firm conclusion of what I have found out.
Conclusion
From the graph I spotted a trend from the line of best fit. The concentration of hydrogen peroxide has an affect on the amount of oxygen produced. During the reaction the yeast is breaking down the hydrogen peroxide into water and oxygen gas.
H202 Yeast H202 + 02
The concentration of the hydrogen peroxide does matter, as it will affect the amount of oxygen produced. If the concentration of the hydrogen peroxide is strong e.g. 1.0 Molar it will contain more particles of hydrogen and oxygen rather than a weak concentration e.g. 0.2 Molar. A strong concentration will produce more oxygen than a weaker concentration. The yeast will be able to break down the hydrogen peroxide depending on how strong or weak the concentration is.
From looking at my graph we can see that when the concentration of the hydrogen peroxide is 0.2 Molar the amount of oxygen produced is 3.2 Cm3 and when the concentration is 1.0 Molar the oxygen produced is 15.6 cm3. These results show that a strong concentration will produce more oxygen than a weak concentration.
I have concluded that the concentration has an affect on the amount of oxygen produced. My prediction I made was correct, which is proved by my graph. My prediction matches my evidence and means I have collected correct and accurate results.
Evaluation
My task did work out well. The reason it was good is because the results I obtained were accurate. This indicates that my task was done correctly. The method I created was done as accurately as possible, just before starting the actual experiment. The procedures must be correct because it is important so that I can obtain correct and accurate evidence. Overall my planning was good as I got through the experiment smoothly and getting the evidence needed, which were fair.
My evidence was accurate as shown by my graph. I drew a line of best fit, which was appropriate. From this I found out that my results show a strong relationship because a couple of points were just off the line of best fit. This proves I obtained accurate results. As the line of best fit was drawn a couple of points were just off it. These anomalies are indicated with a circle around them. These anomalies do not fit in with the line of best fit, which tells me that a human error could of occurred. There are a few possible ways that a human error could of occurred.
✦ Reading the measurement off the gas cylinder incorrectly.
✦ An error in making the concentration.
✦ Measuring the quantities incorrectly.
All these will affect my results.
To improve my method, so that I can obtain more accurate evidence I would add an extra step in between step 6 and 7. As the hydrogen peroxide is put in the test tube then closed with a rubber bung the yeast is injected through the needle. The step I would add is to “remember to do this every time by pouring the hydrogen peroxide in the test tube and inject the yeast through the needle”. This step is important because if both hydrogen peroxide and yeast are put through the needle then they would react and the oxygen produced will escape, making it an unfair test.
My method gave evidence that is reliable and therefore it can always be counted on to be correct. The procedures in my method are accurate and precise. This is important because the method is how to collect reliable evidence. It has all the details on what to do, which are put into easy stages to follow and understand. This is done to ensure reliable evidence to be obtained.
I have obtained enough evidence to draw a firmed conclusion. I did five repeats for each concentration making a total reading of 25. From the repeats I calculated an average result. These results are correct and accurate as shown by my graph and also means that I can draw a final conclusion that is correct.
To improve my plan I could use pipettes to measure the quantities more accurately. If this was done I could ensure more accurate concentrations. If the concentration is accurate more reliable results would been obtained. Another improvement I could do is to do more background research in order to produce a much better plan. I also could of measured the reaction with a different technique.
Further work could have been carried out to get additional relevant evidence. I could of done this investigation by varying the other factors to investigate in that. Different acids and enzymes could have been investigated under the same experiment; from this it will give my conclusion more support.