Fair test
I will do all the experiments on the same day so that the weather conditions and surrounding temperature are the same for all of my results. This is because on another day the weather conditions would be different and would effect the surrounding temperature and therefore effect the rate the water in my experiment cooled.
I will use the same measuring cylinder for all my experiments because another cylinder would measure the required amount slightly different, as they are all slightly different.
I will measure the amount of water in a measuring cylinder from the bottom of the meniscus in all of the volumes of water to make sure I have the correct amount of water.
I will repeat the experiment on each volume three times to make sure there are no anomalies and my results are accurate.
I will use the same thermometer to make sure my results are correct.
Prediction
I predict that the smallest volume will take the shortest time to cool down and the largest volume the longest.
This is because if you have a small volume of water it will have less heat energy than a larger volume of water. This is because a small volume of water will have fewer particles in. As there is less energy it will take less time for the energy to escape and therefore less time for it to cool down. As the molecules on the surface of the water cool fast, convection can take place quicker. I can make this prediction using my background knowledge.
Analysis
The evidence I have collected shows that the smaller the volume of water, the quicker the water cools.
I have plotted the results I have collected on my graph. The points form a curve; this is called a cooling curve. I can work out how fast the water cooled in the first 20 seconds by working out the gradient.
You work out the gradient by drawing a line from 100°c to the temperature at twenty seconds. You then extend the line so it is in line with 100 seconds and draw a horizontal line from the end of this line to the vertical axis. You then count how many °c there is from where the horizontal line connects to the vertical axis to the 100°c point and divide the number by 100. This gives you the gradient or the rate of cooling.
Here are our rates of cooling results:
50ml 0.34
100ml 0.13
150ml 0.15
200ml 0.11
250ml 0.11
As you can see from the graph I have plotted using the rate of cooling results the first twenty seconds of 100ml and 150ml should be reversed. Also 250ml should be less than 200ml. These results can be explained by human error. The stop clock was started either too early or too late on both all these results.
Evaluation
I think that our procedure was accurate and gave us correct results considering that we did not have idealistic instruments as we repeated each experiment three times.
Our results when plotted on a graph formed a reasonable curve except a few anomaly where the result was either slightly too high or too low. I think these anomalies are to be expected, as the equipment cannot be 100% accurate as a computer was not recording the results and the air temperature naturally constantly changes.
I could have improved the investigation by increasing the amount of times I repeated each experiment. In an idealistic world I would have done the experiment in a lab with a controlled air temperature so that the air temp would be exactly the same for each experiment. I would have a probe in the water that started the experiment as soon as the water reached 100°c. I would have a device that would not let the water evaporate until the water temperature reached 100°c. I would have a device that would cut off the heat supply as soon as the water reached 100°c. I would have a temperature probe that recorded the temperature every 100th of a second until the water reached the set room temperature. I would insulate the bottom of the beaker so that heat could not travel from the water, through the beaker and on to the surface that the beaker is resting on.
In the experiment I could have improved the experiment by starting the stop clock exactly on 100°c and using a temperature probe.
I would extent this experiment by changing the starting temperature of the water or changing the air temperature surrounding the water.
