Aim
I aim to plan an experiment to allow me to gather results and record them in a suitable manor to help investigate what the effect of different molarities of HCL has on the speed of the reaction when the reactant is a one cm strip of magnesium. However, before carrying out the main experiment, to get ‘a better view’ of the variables and changes we could make, we carried out a preliminary experiment, the way we hoped to carry out the main one. We did this so that we may analyze the results we gathered from it, look for any anomalies, record these and try to work out what caused them so that we can make future changes to the experiment or influence to the best of our ability, any exterior objects or things that may have helped to cause the anomaly.
For the experiment, the variable that I will change will be the molarities of the HCL, and the variables I shall keep the same will be the amount of HCL in each boiling tube, the time I will record the temperature changes in and the amount of magnesium I put in each solution. The different molarities I will be using are 1, 2 and 3.
Prediction
I predict that the magnesium will dissolve the fastest in the three molar solution as a quicker chemical reaction will take place in it. This would be because it contains the highest concentration of particles (three grams per litre). As the magnesium enters the HCL, magnesium chloride will be formed and hydrogen will be expelled. The resulting reaction should produce heat, which in theory would speed up the reaction as it happens due to the particles moving faster and thus having a much higher collision rate.
I expect there to be anomalies from the results of the trial experiment, and possibly a small amount from the main experiment but a greatly reduced number of them as I plan to try to deal with the causes of the ones that will show in my preliminary experiment.
Method
I will be using the following apparatus: a boiling tube rack, three clean boiling tubes, a thermometer and a stop watch. The reactants are three one cm magnesium strips, and three 10 ml amounts of HCL of different Molars. I will label the different molars from 1-3 in accordance to their molarity. I will then measure the temperature of the HCL in each one of the boiling tubes so I can get a starting point at which to base my recordings on. I will then cut a strip of magnesium tape into three 1 cm strips, put one of the strips in the first boiling tube (one molar) and place the thermometer in it. I decided to take readings at fifteen second intervals for the preliminary experiment. I will then record the temperature six times, every fifteen seconds for each of the molarities. After obtaining the results I will draw up a line graph to display the results in an easy to understand form.
There are factors, which can affect the experiment if no attention is paid to keep them controlled throughout the experiment. I will have to pay special attention to the correct measurements of hydrochloric acid and magnesium strips used in the experiment. If I fail to do this, the whole experiment will contain so many anomalies that it will be literally impossible to draw a feasible graph to display them and come to a conclusion.
I will also have to make sure that the boiling tubes I use are clean by rinsing them with water. I will also have to completely dry them afterwards as not to pollute the HCL with H20 thus effecting the molarity, thus effecting the speed of the reaction.
I decided to gather six results for each molarity so that I may see a reasonably easy to understand graph of results so that I may easily compare them to each other.
If the results do not show a trend, it would suggest to me that I unsuccessfully managed to control one of the vital factors in the experiment. For instance, if the magnesium took sixty seconds to ‘dissolve’ in the 3M HCL solution, I would predict that there was less of it than the others.
For safety reasons I have told that any of the solutions should not rise in temperature about 50 degrees. If it does there is something wrong with either the chemicals I am using, or the way I am using them. If the HCL is at this temperature, there is a high risk of the magnesium reacting in a violent manor with the HCL. Possibly to the injury of me or others around me. I will be wearing safety goggles during the whole experiment.
Results
When looking at the results I obtained from my preliminary experiment, I could see no obvious anomalies. Below is a graph showing the results I obtained from the experiment.
The Starting temperature for the 1 Molar Solution was 27 degrees Celsius. The 2 Molar solution was 24 degrees Celsius and the 3 molar solution began at 24 degrees as well.
I noticed the sharp rise that took place in the temperature of the three molar solution as the magnesium was added to it. The temperature rose two degrees within a period of fifteen seconds. I think that this proves the validity of my prediction and that it was successfully predicted that that higher the molarity of the solution, the sharper the rise in temperature. However, the results from the preliminary experiment should not be taken seriously as it was merely under taken to tell us if any improvements can be made to the main experiment later on.
Changes
The main anomaly I noticed in my results came from the data collected when measuring the rise in temperature with the three molar solution. Near the end where it was expected to keep rising due to the dramatic chemical reaction that took place in it. However, the temperature dropped one degree in the last fifteen seconds of measuring. I believe this was just something that I overlooked in my prediction and is expected to happen. As the chemical reaction takes places quickly due to the molarity, the main temperature rise would be near the beginning, as it was recorded.
In the main experiment I will record my results at time intervals of five seconds instead of fifteen so I can better measure the rise in temperature more accurately. Also this may show up more anomalies, however, as long as my final results show a definite pattern, the anomalies can be discarded.
Also, I will use a two center meter strip of potassium instead of a one center metre strip so that the chemical reaction will last longer in each solution, and therefore I will have the chance to obtain a broader range of results, so I could possibly change them into averages to plot onto a graph fairly.
