This is how my experiment will be set out:
Keeping this experiment a fair test
There are many variables in this experiment that can effect the outcome of this experiment. The dependant variables that I will keep the same will be the height of the tin can above the wick. I will keep this the same because different heights can effect the heat that is transferred to the tin can and into the water, therefore altering the temperature change. I will use the same tin can so that the experiment is fair and that different cans may be of different thicknesses so allowing different amounts of heat through. I will keep the amount of water that I put inside the tin can, the same for each experiment to be fair. I will decide on this amount from my preliminary experiment. The time for each experiment will also be kept the same to ensure the water has had equal amounts of time for it to heat up, again I will decide on the time from my preliminary experiment. The independent variables that I am measuring are the weight of the alcohol in the burner, both before and after the experiment, and also the temperature difference from before and after the experiments. I will also make sure that I take the lid off of the burner as late as possible, only when the burner it to be lit. This is because when the lid comes off a smell is released, so some gas is released which could alter my readings for the mass. This will also apply when replacing the lid after the experiment. I will make sure I keep this experiment fair by carefully controlling the variables.
My Preliminary Experiments
Before I do my actual experiment I am going to carry out some preliminary experiments to help me decide on how much water I should use in the tin, the time I should allow for each experiment and the height above the flame. I will select the most appropriate and the one that gives the best results and best temperature change.
Table from preliminary experiment:
Amount of Water
Height of tin above wick
Temp of water before
Temp of water after
This tested a random alcohol
From these results I have decided to use 150ml of water and time for two minutes per experiment with a height of 5cm above the wick of the burner. I decided this because it gave a good temperature change and is suitable. Using 200ml of water did not give as good of a temperature change and it was quite a lot of water, which did not heat up as much. Also one minute was too short and did not give very good results. Three minutes was also too long for each experiment and the temperature change was large, making the water rather hot so, I decided to use two minutes as a suitable time to give me a good temperature change. Also at three minutes, the hot water could be dangerous and I want to ensure safety. I decided to use 5cm as a height above the wick because 11 and 8cm were quite high above the wick and the heat wasn't really reaching the bottom of the tin can and was being transferred to the surroundings. Also 4cm was slightly too near so I chose 5cm as a reasonable distance.
So from this I will be timing each...