Conclusion and if I could Essay Example for Free

Conclusion and if I could Essay The rate of reaction is the speed that a reaction takes place and how long it occurs for. Chemical reactions only occur when reacting particles collide with each other with sufficient energy to react. The minimum amount of energy required to cause this reaction is called the activation energy. There are different variables to consider when measuring the rates of reaction. These can include catalysts, surface area, temperature or concentration of the liquid. These being changed can either increase or decrease the rate at which the reaction takes place. Temperature: in a cold reaction mixture the particles are moving quite slowly-the particles will collide with each other less often, with less energy, and fewer collisions will succeed to occur. However if we heat the reaction mixture the particles create kinetic energy and will move more quickly-the particles will collide more often. It is hard to measure accurately the temperatures and will be hard to keep precise when obtaining evidence so I wont experiment with the temperature. Concentration: in a reaction where a reactant is low in concentration, the particles are spread out and will collide with each other less often resulting in a slower reaction. If the concentration of any reactant in a solution is increased, the rate of reaction is increased because the particles are more crowded together and will collide more often. Increasing the concentration, increases the probability of a collision between reactant particles because there are more of them in the same volume and so increases the chance of a collision forming products. (slower ifaster, illustrated below). Surface area: large particles have a small surface area in relation to their volume-fewer particles are exposed and available for collisions. This means that fewer collisions happen and therefore the reaction is slower. When we use a smaller solid reactant you are increasing the surface area and that makes the reaction occur faster. If one of the reactants is a solid, the surface area of the solid will affect how fast the reaction goes. This is because the two types of molecule can only bump into each other at the surface of the solid. So the larger the surface area of the solid, the faster the reaction will be. Smaller marble chips have a bigger surface area than larger chips for the same mass of solid. There is not enough variation available for this experiment so I wont do this. * Catalysts: a catalyst is a substance which increases the rate of a chemical reaction, without being used up in the process. It can be used more than once to increase the rate of conversion of reactants into products. A catalyst lowers the amount of energy needed for a successful collision- so more collisions will be successful and the reaction will be faster. Also it provides a surface for the molecules to attach to, thereby increasing their chances of bumping into each other. Catalysts are specialized so different reactions need different catalysts. Prediction: I shall be measuring how the change in the rates of reaction changes when the concentration of acid is changed. This change in concentration will affect the rate of reaction because when acid is diluted there is more space for the particles to move so fewer collisions take place. To make these experiments fair tests, I shall make sure that I measure all reactants and make sure the temperature of the liquid are the same. I shall take great care to make sure that no catalysts are added. I shall also make sure that I use hydrochloric acid taken from the same source to make sure it is as similar as possible but I will be changing the concentration of the liquid but diluting it with various amounts of water. I will be using calcium carbonate marble chips and hydrochloric acid to measure the rates of reaction and I will change the ratio of water: acid to change the concentration. I chose to do preliminary experiments to investigate the best amount of reactants to use in my experiments. I did 5 preliminary experiments and they all came out with various results. I came to the conclusion that 1g medium sized marble chips and 10 ml of liquid gave the best results. After doing the preliminary experiments I think the best result was the experiment that I did last. So I have chosen to use those variables in my final experiment. I think that when I perform my final experiment, I shall receive similar results to my preliminary experiment. To find the best possible outcome, I will repeat each test 3 times and will have 6 differently concentrated acid amounts. The amount of liquid will be the same at all times but the ratio of water and acid will change. I will record each reading at 20 second intervals to reduce an excess of results. Amount of acid(ml) Amount of water(ml) Concentration of liquid % Safety: To make sure the experiment is carried out safely, I will wear protective goggles, I shall tie my hair back, wear an overall. I shall also not sit down by the equipment while the experiment is in progress because if anything gets knocked over, I would have a delayed reaction and it would take me longer to get out of the way.