I am going to change the concentration of the hydrogen peroxide that is mixed with the yeast. I will be using 5% 10%, 15% & 20% concentration of hydrogen peroxide. I will not change the amount of hydrogen peroxide that is used because that will change the concentration levels of the solutions and will make it an unfair test. Increasing the amount of hydrogen peroxide would make the experiment very difficult to measure, and would make the results much less accurate and precise. This is the same for the amount of yeast used in the experiment. The amount of yeast (the enzyme used) added to the hydrogen peroxide will not change because it would make the results gathered invalid.
Independent Variable: Concentration of hydrogen peroxide used in the reaction, changing only one factor will make the results as precise as possible. Dependant Variable: Amount of gas given off from the catalyse during the reaction. The amount of gas produced will vary because the higher the concentration of hydrogen peroxide used the more gas will be produced.
An investigation to show the effect of changing the concentration of hydrogen peroxide on the reaction rate of catalyst.
How will I make my investigation a fair test?
We will repeat the investigation 5 times for every 5, 10, 15, 20 percent of hydrogen peroxide.
Use the same catalyse too so that it is accurate.
Measure yeast accurately.
What it is?
Catalyse; is the enzyme, for our experiment it is yeast.
Substrate; the base of the reaction.
Equipment
To start, our group of four collected all of the equipment. This was:
A test tube with a specific amount of hydrogen peroxide and concentration in for the reaction.
A container half full with cold water for the measuring tube to stand in.
Yeast for the reaction.
Scales to measure the amount of yeast on.
A test tube holder for the test tube to stand on.
A plastic measuring cylinder full of water to see how much water was lost from the oxygen being emitted.
Delivery tube/bung for the oxygen to access through from the test tube to the measuring cylinder.
A stop watch to time the experiment.
An investigation to show the effect of changing the concentration of hydrogen peroxide on the reaction rate of catalyst.
Method
Weigh out 0.59g of yeast on the measuring balance.
Add the yeast to a boiling tube.
Measure out 4ml of hydrogen peroxide.
Fill a measuring cylinder with cold water right to the brim.
Get a piece of plain paper and slip it over the top of the measuring cylinder.
Pick up a water trough.
Fill it half full with cold water.
Get some goggles to protect your eyes.
Get a stop watch to time the length it takes to react.
Get a bung and a delivery tube and attach them to each other.
Get a pipette.
Place your hand over the top of the measuring cylinder.
Rotate it 180 degrees so it is upside down then place it in to the water trough.
Carefully remove the paper from under the tube.
Using the pipette measure out the hydrogen peroxide.
Quickly add the bung to the boiling tube.
Once the bung is secure immediately start timing.
Once oxygen has stopped being produced, stop timing.
Record results.
Repeat a further four times.
Then carry on repeating the experiment changing the concentration of substrate when required.
An investigation to show the effect of changing the concentration of hydrogen peroxide on the reaction rate of catalyst.
What has my investigation shown?
My investigation has shown that as you increase the concentration, more oxygen is produced as the reaction speeds up.
Interpreting my data
Looking at the graph it shows that at 5% there was a reaction until 40 seconds where the gradual gradient stopped, the amount of oxygen produced was 19.5 before it stayed the same for the further 20 seconds, from 40 onto 60 seconds there was a plateau. For 10% there was a reaction until 50 seconds then the gradual gradient stopped, the amount of oxygen was 33.6 when it came to a plateau. However at 15% there was a only a reaction until 30 seconds and it quickly came to a plateau at 74.3 from 30 seconds onto 60. Last of all 20% took off to a sudden start and went all the way up 97.3 at 30 seconds and carried on a plateau to finally end at 60 seconds.
Reliability of my results
Our data was very reliable as the results didn’t vary a lot and the range bars were reasonably close together. All of my graphs show that the speed of the reaction of the first 20 – 40 seconds was much faster that 40 – 60, then gradually levelled out to a steady plateau.
An investigation to show the effect of changing the concentration of hydrogen peroxide on the reaction rate of catalyst.
Analysis
For the 5% and 10% graphs the range bars stayed the same almost throughout both those graphs, however for the 15% graph the range bars started increasing in size and the graph started to go up rapidly in size at the start between 10 and 30 seconds. All my graphs show that the strongest and faster reaction was at the very beginning then started to flatten out into a plateau at around 30/40 seconds, but some varied.
Evaluation
Over all I think my investigation was very successful, we had mostly very accurate results, and the range bars didn’t vary as such. If I had to make a change to do this investigation for the second time I would make sure the same person was putting the bung in the test tube and the delivery tube under the measuring cylinder so it was about the same time difference. I would measure the yeast more accurately as we may have added more or less at certain points which would have caused outliers. We would check that there were no air bubbles in the measuring cylinder. I think that to make my results more accurate and reliable the main thing that would have to be done is to cut down on human errors by making each test as similar as possible to make results more reliable .There isn’t anything else that would change the experiment drastically if it was altered.
An investigation to show the effect of changing the concentration of
hydrogen peroxide on the reaction rate of catalyst.
An investigation to show the effect of changing the concentration of
hydrogen peroxide on the reaction rate of catalyst.
Lock & key hypothesis