I will only start counting the bubbles after 45 seconds because in my preliminary investigation, I found out that before that 45 second mark the bubbles come out to fast to count and there are too many as well. When the time gets to 45 seconds, I will start to count the bubbles then with also my partner keeping an eye on the time, until it reaches 1 minute and 15 seconds on the time, I will stop counting the bubbles and make a note of how many bubbles I have counted. I will count all the experiments with different concentrations when the clock reaches 45 seconds, to 1 minute 15 seconds, so all the experiments will have the bubbles counted for 30 seconds in total. Once the experiment has finished, then I will need to dispose of the piece of liver carefully and spill the used Hydrogen peroxide solution down the sink, and also change the water in tube B as well to make it a fair test. I will then have to do the experiment for each different concentration. The concentrations are shown in the table below.
Variables;
There many variables that I could change in this experiment and
Keep the same. The main variables are;
- Instead of using a piece of Liver I could use a slice of potato
because that contains Catalyse as well.
- I could test how the reaction rate of the hydrogen peroxide
and the Catalyse changes if I vary the PH scale by adding a bit of
acid or alkali.
- I could see if the reaction rate changes by varying the
temperature of the Hydrogen peroxide.
The variable that I am going to use is changing the concentration of the Hydrogen peroxide to see if that has an effect on how much Oxygen is produced out of the reaction.
Fair test;
To make sure I have a fair test, I will have to follow several rules. I will have to make sure that the following are carried out appropriately;
- I use the same boiling tube sizes.
- I use the same delivery tube each time.
- I use the correct amount of water in boiling tube B.
- I use the correct amount of Hydrogen peroxide.
- I do repeat readings for each of the concentrations.
The most important one is that I allow the same time to count the bubbles for each of the concentrations, as this is crucial.
Safety;
For this experiment safety glasses must be worn at all times, as the hydrogen peroxide solution can be dangerous if it gets into your eyes and if it gets in contact with your skin, you need to rinse it off immediately. Your bags, coats and other personal possessions are placed out of the way securely or tucked neatly away under your desks. The Hydrogen peroxide is bleach, meaning that it will either stain or take the colour out of your clothes or bags. Our bags and coats also need to be tucked away because if the liver falls on any of them, it wouldn't be very pleasant to wear, it may even smell bad. I will have to take care and be aware of others around me who are working. After all, safety does come first.
Preliminary Investigation.
For my preliminary work I used a piece of Liver, which worked very well because it has plenty of catalyses to react with the Hydrogen peroxide. I will use Liver in my experiments. In my preliminary investigation, I set up my apparatus like I have shown in my diagram. I used 20cc of the H2O2 to see what happened in the highest concentration. I found out that when I added my piece Liver, it reacted too much with the H2O2, I had to wait until the stop clock reached 45 seconds for the bubbles to have slowed down enough to count them. The bubbles were coming out fast because the piece of Liver had a lot of Catalyse, which reacted with the Hydrogen peroxide molecules by colliding with them. So I have learnt to wait 45 seconds from when I drop the piece of liver into the Hydrogen peroxide to count the bubbles. I then have to count the bubbles for 30 seconds until the stop clock reaches 1 minute 15 seconds.
My main worry is that at the end of the 30 second counting period that the reaction will slow down to much or finish, so there will no bubbles at all coming out. I have also found out that if I use the same piece of Liver for two experiments, in the second experiment, the Liver doesn't react well with the H2O2 because the Catalyse has been used up in the last experiments reaction. I have decided to use a new piece of Liver in every experiment.
Prediction;
My prediction is that when the catalyse inside the liver( the enzyme) reacts with the Hydrogen peroxide( the substrate) the reaction that will take place will be;
Hydrogen Catalyse Water +
Peroxide ………………… Oxygen.
The reaction will take place because the liver containing the Catalyse molecules, will collide with the Hydrogen peroxide molecules. That type of reaction is called a "Chance Reaction" because there is the chance that the H2O2 molecules might miss the Catalyse molecules or they might collide with them.
I think that the higher the concentration of the H2O2, the greater chance of a collision. That is because the higher the concentration, the more H2O2 molecules there are, so therefore the higher chance there is for a reaction. So this is the order in which the most bubbles will be counted, starting with the highest;
5 Volumes
4 Volumes
3 Volumes
2 Volumes
1 Volume
If you change the temperature of the Hydrogen peroxide then I think the reaction will be a lot slower and less, because the enzymes usually work at body temperature which is 27 C. The body temperature is the enzymes optimum condition that it can work in.
Results;
The following table shows my first set of results;
cc = Cubic centre metres
S = Seconds
C = Degrees Celsius
My repeat readings are;
The average of my two results is in the table below;
I am now going to plot a graph using the information and Data I
have collected through my experiments, which are shown in the tables above.
Conclusion;
When I changed the condition of the Hydrogen peroxide, by changing the temperature of it, the higher the concentration the more bubbles came out of tube B. This happened by a "Chance Collision". That means, when I dropped the piece of Liver containing the Catalyses, the H2O2 molecules could have missed the Catalyse molecules. The higher the concentration of Hydrogen peroxide, the more molecules there are and the better chance there is of a collision. A successful collision is when the molecules collide with each other and react.
The patterns in my graph with the averaged results plotted are that the higher the concentration of the Hydrogen peroxide, the higher the number of bubbles. So on my graph I have a vertical line going upwards.
The word equation that took place was;
Hydrogen Catalyse Water +
Peroxide ………………… Oxygen.
The lock and key theory is that every enzyme has a different shape. They break up the reactant e.g. Catalyse by fitting around the Catalyse into the enzymes active site and breaks up the reactant, the enzyme can also be re-used. Enzymes are Proteins. Protein molecules are denatured by high temperatures and extreme PH environments. If a protein is denatured, then the active site into which the reactant fits in changes shape irreversibly so the reactant can't fit in there. That then means that the reactant can't be broken down.
Evaluation;
This experiment may not have been accurate because the pieces of
Liver that I used in my experiment weren’t measured. Another very important point is that there wasn't a method of measuring the amount of catalyse in the Liver. That was the main problem in the experiment.
The size of all the bubbles weren't the same. At the beginning of the reaction when you drop the Liver in, the bubbles come out smaller and faster, I think that happens because they are pressured and pushed out so they break up into little pieces. I did repeat readings which confirmed my first readings. I could extend this experiment by seeing if O2 would displace the water in a beaker with a lid on.
I only got one anomalous result, this happened while using the 5 Vol of H2O2. I got this result possibly because I used a larger piece of Liver in this experiment then the others.
