How Does the Temperature Affect the Rate of Reaction?
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: 2H? O? 2H? O + O? 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.
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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. Hypothesis 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. * Potatoes- We used potato because the celery caused the reaction to be too fast and the results were unreliable. * Knife- We used the knife so we could then cut the cylindrical pieces of potato in to smaller bits so the surface area was smaller. * Scales- This was used to measure each piece of potato to make it a fair test. 100ml measuring cylinder- This was used to measure the amount of gas that was produced during the reaction * Water bath – This is where the experiment took place. * Delivery tube – one end of this was connected to the bung and the other to the measuring cylinder. This gave us accurate results for the gas collected. * Bung- This was used so the gas doesn’t escape during the reaction. * Syringe – I used this to measure equal amounts of hydrogen peroxide so they were accurate. * Hydrogen peroxide- This was the selected acid for the test.
We used this at a concentration o 20% so we could get the most reliable results possible. * Stopwatch- We used a stopwatch to make sure that we timed it for 5 minutes Safety To ensure I, and the people around me were safe during the experiments I had to carry out some safety precautions so no one was in danger. First of all I made sure the work surface was clear of any obstacles and that any chairs were tucked under the table, out the way. I also had do make sure everyone was wearing safety goggles throughout the test encase any of the solutions were knocked and splashed up into anyone’s eyes.
Everyone one participating on the experiments had to make sure their hair was tied back and any jewellery was removed. When we had to remove the measurements of hydrogen peroxide from the water bath, we needed to remove it in a way where we didn’t burn ourselves Actual method 1. First of all, you need to select a potato for you tests and extract cylinders of potato using a core borer. These should all roughly be the same size. I did this because the cylinders are near enough 3 grams of potato that we needed. 2. Next remove the skin from each end of these cylinders o it doesn’t affect the reaction. 3. Thirdly, you need to measure out the 3 grams of potato that you need using the weighing scales. You then have to cut the potato into 9 segments, with a length if 5mm, a radius of 4mm and a diameter of 7mm so you can have complete coverage of the potato, from the hydrogen peroxide. This cancel’s out the possibility of this variable changing and making the experiment unfair. 4. Measure 25ml of hydrogen peroxide, at either 5°, 20°, 40° and 65° and put it into a conical flask. This was decided because it allows the solution to react quickly enough. . You then have to fill the measuring cylinder with water, and then submerge it into the water bath without any of it escaping. 6. Next you need to manoeuvre the delivery tube under the measuring cylinder in the water bath. 7. You now need to place the pieces of potato that you just cut up into the conical flask without misplacing any of them as it may lead to inaccurate results. 8. After you have placed the potato into the flask, you need to place the bung (this is on the end of the delivery tube) on the top of the flask 9.
Start timing with the stopwatch straight away and record the ml decrease of gas every 30 seconds. 10. Stop timing and recording results after 5 minutes. 11. Repeat this method for each temperature, only changing step 4 for each experiment. 12. You must repeat each temperature 3 times. We did this to make our results accurate. 13. You must make sure that the potato is the same weight for each experiment to make you fair, accurate and reliable. Experiment diagram Initial method Throughout my experiment, I will only be changing one variable for my tests, which will be the temperature of the hydrogen peroxide.
The temperatures that I will use will range from 5°C, 20°C, 40°C and finally 65°C for each test. I will test the gas that is collected through the experiment every 30 seconds, for 5 minutes. I will then repeat each test 4 times to make it fair and accurate, then giving me reliable results to evaluate later on. This gives me enough data allowing me not to repeat any more of the tests. Another variable that I could have chosen to change was the surface area of the potato or the catalyst. I decided not to do this because it was too expensive and wasn’t available to me at the time.