To decide how much acid to put in the conical flask I knew that it had to be the same amount every time and it had to cover the marble chip so I decided on 50cm³ of acid as I knew this would cover the marble chip easily and also wouldn’t waste much acid as I would have to use new acid for each experiment.
I decided to use a 1g marble chip, I also found that I could use 0.8-1.2g chips and the result would come out the same. To find this out I did experiments with 0.8g chips 1g chips and 1.2g chips the resulting times all came out the same for these experiments, any more/less weight effected the result.
For the surface area of the marble chips I knew I needed to get them the same shape and size to make it as accurate as possible.
Diagram
Method
- First collect all equipment, a conical flask, a delivery tube, 2 measuring cylinders, a tub of water, a stopwatch, 1M, 2M and 4M acid, 12 marble chips each weighing1gram and also with equal surface area.
- Set up the equipment as above but do not add the marble chips into the acid.
- Make sure there is 50cm³ of acid in the conical flask to make sure you are accurate use a measuring cylinder. For the first experiment use 1M acid.
- Start the experiment, Drop a marble chip into the conical flask then as soon as the first bubble comes into the measuring cylinder press start on the stopwatch.
- Keep a keen eye on how the gas fills up in the test tube as soon as it gets to 20cm³ of gas press stop on the stop watch.
- Record your result.
- Repeat the experiment 2 more times with 1M acid so the results will be accurate and reliable. Use fresh acid every time.
- Repeat the experiment 3 times with the 2M and 4M acid.
- Record Your Results.
Fair Testing
I made sure this test was fair by making sure all of the measurements were the same and the marble chips were the same mass and weight if I had not done this then it could have changed the whole experiment, e.g. if I had one marble chip with a large surface area and one with a small surface area and they both weighed 1gram and were both put into 1M acid, the one with the larger surface area would have the fastest reaction time as it has a larger surface area which means more acid particles will collide with it which will increase the number of successful collisions which will speed up the reaction time. To make sure the temperature didn’t affect the test I did all of my experiments in the same room which is the same temperature every day. I also checked the temperature was 21ºC with a thermometer.
Observations
These are the results I took down while conducting the experiment;
Analysis
I first converted my results into seconds then picked out any rogue results which could effect the graph and conclusion;
In order to make a graph I averaged the results;
I then drew a graph to show how the concentration of acid effects the rate of reaction.
Conclusion
I have found that my prediction is nearly correct. The speed of the reaction nearly doubles each time by a larger concentration of acid, which will have twice as many particles, which will have twice as many collisions which means there will be twice as many successful chemical reactions. The results showed this except they weren’t quite as accurate. They were very close at 2M and 4M but were further apart at 0.5M & 1M. I took readings from a best fit graph and the results were quite close to an ideal set of results except for the 0.5M which was too high and had gone wrong for some reason.
Evaluation
Most of my results were accurate except for the 0.5M results which seemed to go wrong. All of the other results were quite close together except for a few rogue results which could have been caused by a rise in temperature on the day of the experiment or maybe human error such as the marble chip not weighing enough or it weighing too much. I think to make this experiment more accurate I would have to do all the experiments more times, I certainly would also have to do the 0.5M & 1M tests again if I wanted this experiment to become more accurate.
