- 100ml Measuring cylinder = to collect the hydrogen bubbles so I can measure and collect results.
- Stop clock = counts the time in the reaction.
- Marker pen = to mark the level of water every 10 seconds.
- Magnesium 3cm strips - one of the reactants in the chemical reaction.
- Safety Goggles = to protect my eyes.
- Hydrochloric acid - one of the reactants in the chemical reaction and in different mols in suitable ranges of concentrations; 1.0, 1.2, 1.4, 1.6, 1.8 and 2.0. This shows the different rates of reaction as you change the concentrations.
Variables:
Independent variables = Concentration of acid will be changed throughout the experiment.
Dependant variable = Volume of hydrogen (H2) produced will the factor we will look at, at the end of the experiment.
Controlled variables = ① Amount of magnesium will need to be kept the same length & width and the same surface area because you need to keep it a fair test.
② Volume of acid will be kept the same to ensure that the results will be reliable.
③ Test tube temperate needs to be kept the same because if the temperature increased, the reaction would be faster and would cause inaccurate results.
Preliminary Work:
I did a preliminary test where magnesium and hydrochloric acid were mixed together to cause a reaction. This helped me to work out the optimum length of ribbon and the volume of hydrochloric acid I should use. From my results, I decided to use 3cm strips of magnesium and 15ml of hydrochloric acid. I did use a measuring cylinder 50ml to measure the amount of hydrogen bubbles in my preliminary work but decided to use 100ml in this experiment. As there were too many hydrogen bubbles and exceeded the volume of the cylinder.
Plan:
I will conduct the experiment by reacting magnesium and hydrochloric acid. This reaction will produce gas which I will carefully collect and measure. Firstly I will get all the equipment I need and make sure it is safe. The reaction will begin when I insert the magnesium ribbon. This reaction will give out a lot of gas and my objective is to collect this gas. I will completely fill a measuring cylinder with water and then place it upside down inside the trough, which has already been filled with water to the rim. The test tube with the reactants has a delivery tube on the side which I will insert into the measuring cylinder. To start the experiment I have to put the magnesium and acid in the test tube. When I put them together I will quickly place a bung on the top of the test tube so no gas can escape. Also as soon as the magnesium and hydrochloric acid react I will start the timer.
The gas should travel to the top of the test tube and travel through
the delivery tube to the measuring cylinder. The gas will rise to the top of the measuring cylinder and as the gas collects, the water inside the cylinder will be pushed down so I can see how much gas is collected in there. Each experiment will take 1 minute and in that time I will be recording the amount of hydrogen lost every 10 seconds. But to see if my prediction is right I will use 5 different concentrations. So instead of 1.0 mols of acid, I will use 1.2, 1.4, 1.6, 1.8 and 2.0. To make our results even more accurate I will repeat each of the experiments 3 times. At the end of the experiment I will clear away all equipment and make sure
Results Table:
Conclusion:
In conclusion, from my results gathered from my table and graphs my initial prediction was correct. The higher the concentration of the hydrochloric acid, the faster the reaction. In all my graphs, there was a positive correlation and there is a curve on my graphs which means that it is indirectly proportional because if it was a straight line it would have been directly proportional which means the rate of reaction would have doubled every time.
I put gradients on every graph so I could compare the steepness on the line so I could conclude my results. I found that when the concentrations of acid became stronger the gradients became higher. Graph 1.0 mols had a gradient of 1.55 and 2.0 mols had a gradient of 3.33.
Evaluation:
We didn’t encounter any major difficulties during the experiment. Except high concentrations of acid were split however this didn’t not lead to inaccurate results as we restarted the experiment.
If I was to do this experiment again I would use magnesium power, this would mean more surface area. I could then find out if there was more surface area, would this make the reaction faster or effect it in anyway.
To improve my experiment, I would make it more accurate. I would do
this by using a more precise measuring tool. I believe that this would
have made the experiment a lot fairer and accurate. Also, I could
improve it by making sure that the beakers were all dry before I put
the Hydrochloric acid into them. This would have given me a more
specific result. For safety I would of wore safety gloves so if acid came into contact with my hands, it would not harm them.
I believe my process of collecting results were fairly good. I took a lot of care and planning during the tests. The qualities of the results were fairly reliable as all my investigations showed more or less the same results and the trend line was good fitting. This shows that my initial predictions and theories were proved right. I didn’t find many faults in the results (outliers) and most of the results fit the pattern. However there were minor results that did not fit the trend line and most of were probably the fault of equipment or bad timing. The amount of scatter on my graphs is very small because there isn’t a wide range in the error bars. My error bars ranged at the most at 3cm³ (on graph 1.2 mols). Our best results was graph 2.0 mols because it had fairly small error bars, the reason for this is because we were more accurate in measurements and timing.
I repeated each concentration 3 times to ensure that I can get a good
average and so that I can effectively show and prove that my prediction is correct. As predicted the average results show that the initial rate of reaction increased as the concentration increased which meets my initial prediction of the whole experiment. This shows that I am confident that my data is accurate and reliable. I think I chose a suitable range of acid concentrations because going up in 0.2 stages shows more specific results. In further experiments I may use weaker or stronger concentrations. I wouldn’t use any concentrations too high because this may become dangerous and unsafe.
To extend my work even further, I could have gone lower in the concentration or higher. Also I could have gone to just water to check if there was a trend in the results. There is enough evidence and information to support a good conclusion from this experiment but if I had conducted more experiments with more variables like temperature and different materials, I could have created an even more extensive and interesting experiment.