Bibliography
I gathered this information from: Microsoft Encarta ’95 and The Dorling Kindersley.
Equipment List
Electric Scale, Boiling Tube, Burette, Thermometer, Bunsen Burner, Beaker, Black Card, Safety Goggles.
Equipment Diagram
Prediction
I predict that from this investigation
The Results Table That I Will Use
How Am I Going To Make It A Safe Experiment?
In this experiment I will have to make sure everything is done with safely.
- Throughout the whole experiment I will make sure that I wear safety goggles.
- Also I will make sure that everyone keeps a safe distant away from the flame of the Bunsen burner.
Method
At first I will put on my safety goggles. I will then weigh exactly 10.1 g of potassium nitrate directly into a clean boiling tube. Then using a burette I will add 8.0 cm³ of distilled water. After that I will place a thermometer into the boiling tube and leave it there for the rest of the experiment. I will then heat the mixture carefully using a Bunsen burner. I will make sure that I hold the boiling tube at a 45º angle above the Bunsen burner and keep it at a level distant. I will then allow the mixture to cool in the air whilst stirring it with the thermometer. In addition to speed up the cooling process I will immerse the mixture in a beaker of cold water for a short amount of time. I will still continue to stir the mixture and then place a piece of black card behind the tube so I can clearly see when the crystals appear. Once the crystals appear I will note the temperature to the nearest 0.5ºC. After recording the results in my table, I will then add a further 2.0 cm³ of distilled water to the mixture in the boiling tube. I will then repeat the heating process to obtain a solution and then repeat the procedure to find the temperature at which crystals first appear. Altogether I will repeat the process 4 more times so that I have a set of 5 results.
Results
The results I gained from the experiment are shown in the table below.
Analysis
When I analyse my Volume Of Water Against Temperature graph I found out that the solubility of potassium nitrate at 50ºC is 8.51mol dm-3 of water. When I analysed my Log 10 Ө Against 1/T graph I discovered that the enthalpy value for the solution of potassium nitrate in water was 19113KJ mol.
Evaluation
When I carried out this experiment I believe I did it in a careful and accurate way because I stuck to the instructions given. I could have improved my experiment in many ways. I, who could not have known the exact level of water in the burette, made the reading of water from the burette. So if I had used more precise equipment I could have had more accurate results.
An improvement I could have made in this experiment was to first have done a preliminary study to find any mistakes I made and find a way to over come them. Another way of improvement could have been repeating the experiment 4 more times so that I had 5 sets of results and could have used the average results to work from. This would have pointed out any anomalous results and any mistakes I could have made in one of the experiments.