Patterns of Behaviour Essay

To form a reaction the particles must collide in high speed. The faster the particles collide the more kinetic energy is produced. This produces a bigger reaction. There are five key variables that affect the rate of a reaction (in this case with a solid and a solution): Change in temperature An increase in heat energy within the particles leads to more kinetic energy. Therefore there is more collision of particles and it increases the rate of the reaction. When we decrease the amount of heat energy, this will evidently slow down the reaction. For example we slow down the process of our food rotting by placing it in a fridge or a freezer. Change in concentration The concentrations of acids are classed in molars, so 2m would quite a strong concentrated acid, 0. 5m would be a very dilute weak acid and 1m would be in between the two. Also, the more concentrated the acid, the more particles it contains, so there is more of a chance for collisions.   Change of particle size Increasing the surface area of the particles would lead to more collision. We do this by making the particles smaller. For instance peeling a large potato would not take as long as peeling four small potatoes; this is because the smaller potatoes have a larger surface area for you to peel. Pressure (for gases only) Increasing the pressure would bring particles closer together so there would be more of a chance for collision.   Catalyst A catalyst lowers the activation of energy required, consequently there being a faster reaction. The three variables we are choosing to show which effect the rate of reaction in our experiments are: Particle size Concentration   Temperature Pressure was inappropriate to use as a variable, because we were not using two gases and a catalyst was unsuitable to use for small tests like these. I think that the tests in changing the temperature will have the fastest times, as the hotter a solution is the more the particles will move and collide, thus the rate of carbon dioxide being produce will be faster. I also think that the large particles test will take the slowest amount of time because of the lack of surface area and the reverse will occur with the test with powered calcium carbonate. Plan We will be running a various number of experiments to prove what effects the rate of reaction with calcium carbonate (marble chips) and hydrochloric acid. The balanced equation for these reactants along with the products: Calcium carbonate + hydrochloric acid calcium chloride + carbon dioxide + water Ca Co + 2 HCl Ca Cl + Co + H O When experimenting with the effects of the particle size we will use three sizes: large marble chips, small marble chips and powered calcium carbonate. For the tests in concentration of acid we will use 2m, 1m and 0. 5m. We will use 50cc of hydrochloric acid in each test to guarantee precise results. Finally for the experiments with the changes of temperature we will be heating the acid using a bunsen burner for two temperatures: 30i and 40i , then leaving the acid at room temperature (around 22i ). We will measure the temperature accurately using a thermometer. These will be the only three things that we are going to vary, to explain what affects the rate of reaction. We will also only be testing one variable at a time. For example, in the test for concentration we will obviously be varying the concentration of the acid (0. 5, 1 and 2m) but we will be keeping the temperature and the particle size the same (room temp. and small marble chips). To tell us what actually affects the rate of reaction we will monitoring how fast carbon dioxide is given off. To find this out we will have a plastic basin containing water. A test tube measuring 10cc filled with water will be held upside down in the basin of water and a delivery tube will be attached to the beaker holding the acid and calcium carbonate and the other end will be positioned in the test tube in the water. We will use all the same apparatus to ensure everything is fairly tested and is accurate to the equipment we are using. As the acid reacts with the calcium carbonate, carbon dioxide is released. This will travel through the delivery tube and into the test tube. The test tube will fill up with carbon dioxides and the water will pushed out. We will be timing this with a stop clock. As the water descends to 1cc we will record the time, then at 2cc, again at 3cc and so forth. At the end of each experiment we should have 10 times recorded. For each factor, instead of just performing the experiment once, we will repeat it three times to provide us with a more accurate end result. In total we will be doing 27 tests to show what effects the rate of reaction. Diagram To make certain that this method is good enough and to certify that it worked properly we will carried out a trail experiment. We used all the average variables for fair testing. So the temperature was at room (22i ) the concentration not to strong or weak (1m) and the small marble chips. Trial experiment results 1 molar room temperature small marble chips Min/sec 1cc 1:41 2cc 3:15 3cc 4:46 4cc 6:13 5cc 7:35 6cc 9:03 7cc 10:34 8cc 11:56 9cc 13:27 10cc 14:33 The carbon dioxide was released very slowly in this test. It took over fourteen and a half minutes for it to finish and this would not be practical because of the limited time been given to conduct all our experiments. It took so long, because we had only put one small marble chip in. There were no more calcium carbonate particles to react with the acid particles, so this had a dramatic effect on the time. On In each test we do we will always place more particles than the amount we need, so there is excess calcium carbonate at the end to make sure it does not run out during the test. Because this was the first time we were trying the tests out we were a bit slow placing the bung on and maybe some of the carbon dioxide had escaped. To improve our main experiments to achieve accurate results we had to place the bung on as soon as we dropped in the calcium carbonate to make sure no carbon dioxide escaped. Results Concentration 0. 5 molar room temperature small marble chips 1st 2nd 3rd Average Temperature Room temperature 1molar small marble chips 1st 2nd 3rd AverageAnalysis On the concentration graph the average of the 0. 5m results was looked very different compared to the 1m and 2m averages. Because it took the longest time to reach 10cc of carbon dioxide, the gradient of the line of best fit sloped very gently. The release of carbon dioxide started off very slow at the being. It took 1:30 minutes to reach 1cc, then the rate quickened and in 2 minutes 5cc of carbon dioxide had been given off. On the graph the gradient in those two minutes steepened. The rate slowed down after that and the release of carbon dioxide was gradual and steady.