The equipment I will use is:
- Hydrochloric acid
- Sodium Thiosuphate
- 2 x Measuring cylinders
- 2 x Test tubes
- stop clock
- 2 glass beakers
- 2 thermometers
- Bunsen burner
- water
- tripod
- heat mat
- gauge
- paper with pencil cross
I will make sure my results are accurate by referring to graphs, e.g.: if one point is greatly out of alignment, it should be repeated.
Also I will make sure that the meniscus of the hydrochloric acid and Thiosuphate is flat and not to one side of the test tube or measuring cylinder.
I will take five measurements with a 10 gap interval and I will repeat this twice and take an average to make my results more accurate.
Back ground Research – Trial Experiment
I conducted a trial experiment to find out the correct quantities of sodium thiosulphate and hydrochloric acid for the main experiment. We were aiming for the cross to disappear in around one minute.
We found the more hydrochloric acid the slower the X disappeared. Therefore I have decided to use 25 cm of sodium thiosulphate and 10 cm of hydrochloric acid.
Results
Results
* Because of time problems, we changed our experiment to:
Method
- Set up diagram
- Hold Sodium Thiosuphate over the Bunsen burner until its at desired temperature, use thermometer to check
- Keep acid at room temperature
- Repeat the rest of the experiment the same, except only do once not twice.
Obtaining
I have made enough readings although it couldn’t have been repeated I made readings at more regular intervals, they were taken every five; ten measurements were taken in total.
My results are very accurate I measured the amounts at eye level on the desk, so the meniscus would have been straight and not to ones side; however I found it hard to pour in the two substances into the beaker at the same point with each reading. I also tried my best to get the temperature as accurate as possible, because this would change the reaction rate I have put the actual temperature clearly into the above table, along with the time taken.
Analysis
I have drawn a results table; this clearly shows my results and makes it easier to relate to the graph.
I have drawn a graph to show a line of correlation between the time taken to react and the temperature. I have noticed that the points on the line are a smaller time as the temperature increases. This again goes to support my predictions.
I predicted that the reaction rate would increase because the particles would be moving more quickly which would make more collisions. Also the particles would have more energy so the collisions would be more successful!
M y results proved that my predictions were correct, e.g. as the reaction rate got bigger the time taken got smaller. My graph shows this:
Temperature in° 55 Time in seconds 14.64
45 20.39
35 28.78
Evaluation
Factors that could have made my results less reliable and unfair are:
The equipment, measuring cylinders are mass produced and are not 100% accurate, also the thermometers are very difficult to read accurately. Also the experiment was spread over 2 separate periods so the concentration of the substances used could be different in each one. The equipment was rinsed with tap water after each test; this contains impurities which could effect the concentrations. Also, each time the conical flask is used; it becomes cloudier, making it more difficult to make out the exact point when the cross would disappear, the temperature of the hydrochloric acid was not being monitored, and as a lot of heat from Bunsen burners was being created, the room temperature may have changed throughout the experiment. All these factors will have affected the experiment and made it more bias. These could be areas to work on in the future. Overall I think my results were reliable as these problems are minorities!
I received once anomalous result, but quickly redid the test and my result became normal, I noticed this because it didn’t fit into the pattern my results were forming.
Overall I feel my experiment turned out well. However I could improve my investigation if I was to do it again by spending more time in getting the temperature exact to the designated one, but I do feel that my results were close enough and didn’t cause much inaccuracy in the experiment.
To extend my investigation I could investigate by using different substances and concentrations. I could also investigate the temperature of the hydrochloric acid in the experiment and use a larger range of temperatures, for example investigate beyond 60 and before 15 degrees; this would give a wider view on the experiment making it more accurate.
