The collisions between the particles cause the reaction to take place so the more collisions the greater the reaction rate.
ENZYME AND PARTICLE THEORIES
These two theories will give us an insight into why the reaction happens and the way it occurs to produce greater reactions.
Enzymes
A number of chemical reactions take place in our bodies every day but for the reactions to take place we need to have an enzyme. Some enzymes make these different reactions happen at faster rates, the chemicals that speed up reactions are called catalysts.
Enzymes come in two different forms these are called breakers and builders. Breakers break down larger molecules into smaller molecules this is the process that is occurring in our experiment when the potato is added, as it is breaking down the hydrogen peroxide to form water and oxygen. The other enzyme is a builder this helps the smaller molecules join together to make large molecules.
Another enzyme-controlled reaction besides the one we are doing is shown below
Maltose
Maltose (substrate) Glucose (product)
(Enzyme)
In our experiment the hydrogen peroxide is the substrate the potato or catalase is catalyzing this particular reaction and the product is oxygen and water.
Most metabolic reactions like this one are reversible and can be changed back.
There are 5 important properties that enzymes have
- Enzymes are always proteins
- They have a specific action – different enzymes will not do the same job and only concentrate on specific reactions
- Enzymes can be used again as they aren’t altered.
- Enzymes can be destroyed if heated to a high enough temperature this is called denaturation.
- Enzymes are also sensitive to P.H. intracellular enzymes work best in neutral conditions.
Particles
Chemical reaction rates vary depending on the concentration and temperature and catalyst. For my experiments I changed the concentrations of the solution.
In solutions with higher concentration the reaction rate is greater because the particles are closer together and they therefore have a greater chance of colliding.
Where the solutions were weaker i.e. a mixture of solutions the reaction times would be slower as the liquids are moving at different speeds and the molecules collide in different ways, example glancing blows, which does little harm to the catalyst. Also at higher temperatures particles move faster so more collisions take place and they are more energetic so the reaction is faster.
Chemical reactions also cause atoms to be rearranged by joining or separating to be able for atoms to join, a collision has to take place but this by itself wouldn’t be enough. Bonds between atoms must be broken and new ones formed but this means that it takes a lot of energy for a successful collision to occur. This means there is a certain minimum energy needed before a reaction from a collision can occur this minimum energy is gained through higher concentration or a higher temperature.
DETAILED PLAN FOR PRELIMINARY EXPERIMENT AND FINAL RESULTS
We will use…..
- Potato and Hydrogen peroxide
This equipment will be set up as shown below
We will use 4g of potato and add it to different amounts of concentration of hydrogen peroxide.
- 30ml hydrogen peroxide 0ml water
25ml hydrogen peroxide 5ml water
- 20ml hydrogen peroxide 10ml water
15ml hydrogen peroxide 15ml water
- 10ml hydrogen peroxide 20ml water
The ones marked with a bullet point are the amounts we used for preliminary testing.
The amount of oxygen produced will be measured by using a measuring cylinder this will give a result of the amount of oxygen released which will then be used to show the rate of reaction through a simple equation.
Fair testing
Fair testing is an important part of the experiment to make sure that no inaccuracies occur within my results.
I will change only one variable I have decided that this will be the concentration, therefore I must not change anything else in this experiment otherwise I will get wrong results that show what happens when two things are changed rather then just the concentration.
PRELIMINARY TESTING
We did a preliminary test to make sure that the experiment was suitable and safe to use. We make sure that the concentration of hydrogen peroxide to water was enough to show results at all levels of hydrogen peroxide. We made sure of this by testing at high, medium and low, 30mls, 20mls and 10mls. We also needed to make sure that the materials used were suitable. We realized we needed to improve certain parts of our experiment so that we could get the most accurate results possible.
We are going to change the measuring cylinder; this is because the cylinder we used didn’t have a suitable scale as the results shown at 1-minute intervals were less then the scale that started at 10mls. Also we are going to change the time scale 10minutes as we feel this is amore suitable place to stop as some of the reactions were still taking place at 6 minutes.
For our final experiment we need to have 5 results and the other amounts of hydrogen peroxide will slot in between these amounts.
The results shown give an example of what we will get in the final experiment, that less hydrogen peroxide will produce less oxygen.
CONCLUSION
As I predicted the rate of reaction increases as the amount of hydrogen peroxide increases this is shown on the colour graph where all the results are placed on the same graph to show the relationship between the ratio of hydrogen peroxide and water with the amount of oxygen produced. Although some of the results could have been affected through unfairness we tried to keep the experiment fair and although we had a few anomalous results, our results were effective in showing what we set out to achieve.
These results have been shown because as explained in more depth in the particle and enzyme theories the more particles and enzymes the quicker it is to breakdown the hydrogen peroxide by adding a catalyst, which in this case was the potato. It also involves the greater concentration of hydrogen peroxide which as it increases causes more particles to be able to collide also causing the rate to increase.
However the results I got also showed another relationship between the concentration and amount of oxygen produced this is shown in the final graph and on my results table the connection between the two is that after 10minutes in both experiments when the reaction is ending if half the amount of hydrogen peroxide is used then the final amount of oxygen produced is also half i.e. 30mls hydrogen peroxide to 0mls of water the final amount of oxygen produced is 19.5, now when you half the 30mls to 15mls hydrogen peroxide to 15mls water then you find the amount of oxygen produced is also half as the final result is 10. This shows that the two things are proportional to one another.
EVALUATION
What I predicted before the experiment was quite accurate. I predicted that as the concentration of hydrogen peroxide increased so would the rate of reaction. I feel the accuracy of my results were fairly good but for the 20mls of hydrogen peroxide to 10mls of water I think that between 3 minutes and 8 minutes the results don’t fit the pattern. I can see this as the results show that more oxygen was produced while the expected results would have been less however towards the end the results level out and go against the expected pattern.
To improve the experiment I would change a number of things. Although I felt at the time that it was accurate but I have since realized that these are things I could have improved.
I would have made sure that I did the experiments more times because there would have been a better average. Also to get a more accurate set of results I would have made sure that no water had escaped from the measuring cylinder and made sure that I double checked everything making sure that only the one variable was certain to change.
RATE OF REACTION = FINAL TIME
AVERAGE OXYGEN PRODUCED
