The variable I am going to change is temperature. I will keep all other factors constant to make the experiment fair and so the results are reliable.
Reasons for doing a pre-test
I am going to perform a pre-test so that I have an idea of the quantities of Sugar and water I will need to use in my actual experiment. Doing a pre-test means I will get a more accurate result when it comes to do the actual experiment.
Pre-test method
Apparatus
- Glass Beaker
- Measuring cylinder
- Tripod
- Bunsen Burner
- Stirring Rod
- Thermometer
- Stopwatch
- Heat proof mat
- For safety: Goggles
- Weighing scales
- Gather equipment and set up as shown below:
- Choose your temperatures (I am going to perform the pre-test with the temperatures 20°C, 40°C and 60°C)
- Measure 10g of sugar and 100cm³ of 20°C water
- Pour the water and sugar into the glass beaker and start the clock.
- Stir constantly until the sugar is dissolved and then stop the clock
- Record this time in a results table
- Repeat this experiment again for a more accurate result
- Then repeat the experiment twice with the other temperatures (Remembering when using the Bunsen burner to wear goggles)
- Create averages for the results
Pre-test results
Pre-test Conclusion
My pre-test worked very well and the amounts I used of sugar and water I chose worked so well I have decided to use them in my actual experiment.
Prediction
I predict that in my experiment when the temperature is raised the sugar will dissolve quicker. I believe this will happen because when the temperature is increased the water gains heat energy and the particles gain this energy, which they convert into kinetic energy, causing them to move much faster. This means that there is a higher chance of collision because the sugar and the water particles move towards each other much faster, allowing a head on collision. This collision is when the water breaks down the sugar and dissolves it.
Method
The apparatus and method are no different to the pre-test only this time I will test for 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C and I will repeat the readings as before.
Results
Conclusion
As I expected, when the temperature was raised the quicker the sugar dissolved. For example at 30°C the sugar was fully dissolved at 46 seconds, but as the temperature rose to 50°C the time taken for the sugar to fully dissolve was much shorter at 31 seconds and again as the temperature rose to 80°C the time taken to dissolve was shortened once again to 20 seconds. This is because when I increased the temperature the water and sugar molecules gained more energy, which they then converted into kinetic energy. The particles moved much faster and there was a higher chance of a head on collision so therefore the time taken for the sugar to dissolve decreased when I increased the temperature.
Evaluation
My experiment went as planned. The temperatures and quantities that I chose to use worked very well in the experiment. Although I took care in keeping all factors the same for a fair test and I repeated the experiment and worked on the averages of my findings. I still found two anomalous results when I plotted my graph. I think this Is because of my rate of stirring could not be kept constant. To improve the experiment I could stir only 10 times instead of stirring constantly throughout the dissolving process. I also think to improve my investigation further I could repeat the readings a third time and therefore I would have a more accurate average. A way to extend my experiment is to test how long the sugar would dissolve if it had a larger mass. I think this experiment was carried out with great care and the instructions were followed to the best of my ability.
