How Does the Temperature Affect the Rate of Reaction?

Topics: Chemical reaction, Reaction rate, Oxygen Pages: 12 (3650 words) Published: April 25, 2012
Biology coursework

How does the temperature affect the rate of reaction?

For our experiments, I was investigating what affects the rate of reaction. We used Hydrogen peroxide to test the rate of reaction, with the temperature of this being our variable that we changed. Hydrogen peroxide is a clear, colourless liquid which has various amounts of uses within the laboratory, industrial purposes and even in our households. It is mainly used for cleaning products and hair dye but is also used for paper making. Hydrogen peroxide is made up of two oxygen atoms and two hydrogen atoms. The chemical formula for this is H₂O₂. Catalyse is the enzyme that breaks down hydrogen peroxide which converts the hydrogen peroxide to hydrogen and water. The chemical equation for this reaction is:

2H₂O₂ 2H₂O + O₂
The catalyse that we used is potato, and is the enzyme that I used in the experiment. This enzyme is a protein which speeds up the rate of the chemical reaction, every enzymes does this.
There were various amounts of variables that we could have changed for our experiment. These variables were: to put in a catalyst, to change the surface area of the catalyse, the temperature and the concentration of the hydrogen peroxide. I also had the choice of either potato or celery. I chose to change the temperature of the hydrogen peroxide our preliminary test showed us it would be the best possible way to test the rate of reaction. This variable gave us plenty of results that were reliable as well as accurate.

What can affect the rate of reaction?
There are four different variables that I could have changed to lead to the rate of reaction being affected: temperature, concentration, surface area and the use of a catalyst. Catalyst- This is a substance which alters the rate of a chemical reaction but is chemically unchanged at the end of the reaction. This means that there is just as much catalyst at the end of a reaction as there was at the beginning, and are used again and again. Because catalysts work so rapidly and are used again and again, it is only necessary to have very small quantities of catalyst present to make a chemical reaction go faster.

Temperature- When you increase the temperature, the rate of reaction also increases. When this happens, two chemicals react and their molecules have to collide with each other with sufficient energy for the reaction to take place. These two molecules will only react if they have enough energy. By heating this, you will increase the energy levels of the molecules involved in the reaction. Increasing the temperature means the molecules move faster. But when the temperature gets to a certain point the reaction gets slower and eventually resulting in the reaction to stop.

Surface area- If the potato we used was blended or cut into fine pieces the reaction would have occurred quickly. This example would produce a faster reaction than a large solid, with the same mass but a larger surface area. Increasing the surface area will increase the chances of collisions that will take place.

Concentration- If the concentration is greater there is a higher chance that molecules will collide and speed up the rate of the reaction. If it a less concentration, there will be fewer collisions and the reaction will probably happen at a slower speed. 

For reactions that involve gases or liquids, when you increase the concentration of the reactant, the reaction rate also increases. When the concentration is higher, the chances of collisions are greater.

I predict that when the temperature of the peroxide is increased,the reaction will occur a lot quicker. This will then lead to a higher volume of gas that gets produced, but if the temperature increases too much, it will cause the results to level off and then the enzyme will denature.

Equipment list
* Core borer- This was used to get equal size cylinders of potato so the test would be fair. *...
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