Investigation of Surface Area: Volume Ratio and its effect on Body Temperature

Apparatus

2xMats

5x Beaker with thermometers

x Water Heater

In the experiment a 500-ml beaker was filled with hot water, along with other volumes at 60 degrees. 60 degrees is used because it is quite high compared to room temperature. The apparatus was then set up and the temperature in degrees centigrade was taken every 1 minute, for 15 minutes, with the thermometers in the beakers. The results were then noted. The variable factors need to be considered in order to make the test a fair one. If the variables are not the same in both the beakers inaccurate results will be given. For starters the temperature of the air needs to be considered, within reason. The colour of the flask needs to be considered (a black flask will absorb heat), if there is a colour. The depth of the thermometer needs to be the same in all the beakers. The temperature and amount of the water in the beakers before the experiment starts needs to be the same in each experiment.

It was decided that there should be three tries at the experiment. The first will comprise of the temperature of all the different sized beakers, 800ml, 500 ml, 300ml, 200ml and 75ml, beakers being taken every minute for 15 minutes overall. The next two will be repeats of this experiment to see if it is accurate, if any of the results are anomalous then they will easily be identifiable.

Heat Loss per Minute Calculations

Formula = temp at 0 mins - temp at 15 mins divided by 15

) 100 ml: 72- 57/15 at 1 degree per minute

2) 500 ml: 74-66.5/15 at 0.5 degrees per minute

Analysis

In my prediction I stated that the 100-ml flask would lose heat 2 times more quickly than the 500-ml flask, and the rest are in the middle. The results to my heat loss per minute calculations back up this prediction as the heat loss per minute of the 100 ml flask was 1 degree centigrade whereas the heat loss per minute of the 500 ml beaker was 0.5 degrees centigrade

Conclusion:

My results show that as Surface Area: Volume goes up the heat-loss rate goes down. This means the 75ml beaker lost more heat in the same amount of time than the 200ml beaker, and the 200ml beaker lost more heat than the 500ml beaker in the same time and so on. My results also show that as the water gets cooler it losses heat slower. These results support my plan and also show me other things I didn't mention in my plan. All my results support my conclusions and I don't have any results which don't "fit in" with the rest of the experiment. These results are as reliable as I could make due to restrictions I had, E.G. time limits, and the materials used, the results may have had a degree of inaccuracy. On the whole they are fairly reliable and I think they are sufficient to support a firm conclusion, although the start temperature for the 2nd set of results was a little higher than it should have been. This could have been due to the water cooling on the other set of result before its temperature was measured.

There are many sources of possible error such as human error, which could have been made any time during the experiment take temperature etc... Another factor effecting the results are the smaller the beaker the smaller the thickness of the sides of the beaker, i.e. the 500ml beaker side is much thicker than the 75ml beakers side and the 200ml beakers side size is roughly in the middle. This would effect the heat lost out the sides of the beakers, the 75ml beaker is going to lose heat quicker out the sides than the 200ml and 500ml beaker is. So to make this a fair experiment you would have to use beakers of the same thickness.

Also due to time limits I was only able to collect three sets of results for each beaker when insulated. I think I have enough to support my conclusion but I could have made it a lot more reliable, by doing it a few more times.

I could have used two different sets of apparatus to see if one of them was wrong, due to contamination or error in the beakers.

Evaluations

The evidence I obtained was sufficient to corroborate my predictions. As the results were averaged and all variables were considered there were not really any anomalous results. However one error that was made was that the start off temperature for the 100-ml beakers was 72 degrees whereas the start off for the 500-ml beakers was 74 degrees. This error occurred because the timing of the 100 ml test tubes began too long after the beaker had been removed from the water heater. My results were very reliable as all variables were considered and the temperature readings were taken every minute exactly. I would make the following improvements on the experiment: 1) Set up two beakers of each volume at the same time. In my experiments half of the beakers were done one day and on the next day the other half of the beakers were done. This meant that a direct comparison was not achieved as the room temperature on the first day differed from that of the second day.

2) Use apparatus that measures water with more precision. The beakers that we used did not have very accurate markings on and so it was possible that we put too much or too little water in.

3) Heat the beakers above 60 degrees as they lose

heat quite rapidly and so the start off temperature will not be 60 degrees unless you heat the water to a higher temperature.

If I was going to investigate further I would try different sized beakers. I would also investigate other factors that affect heat loss such as shape of object. I would also investigate how different air temperatures cause differentiation in heat loss.

Alastair Binding

28/06/01

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