Preliminary Experiment:
Aim and Method:
For my preliminary experiment I wish to determine a suitable length of time in which to take results and also to determine an appropriate temperature to heat the water to. To do this I am going to measure the gradual decrease in temperature of the water in one test tube heated to 50 ºc during intervals of 30 seconds.
Results and Conclusion:
From the results (although they were measured and recorded too inaccurately to display here) I have decided that the conditions specified above were suitable, and that the temperature shall be measured over the time period of 10 minutes.
Plan:
Method:
For my experiment I will be measuring the effect the amount of test tubes clustered together has on the rate at which their temperature decreases. To do this I will perform five experiments, each one a variation in the number of test tubes ‘clustered’ together. For the first experiment I shall use one test tube, for the second five, for the third seven, for the fourth thirteen and for the fifth 19. This is because these values fit neatly with the test tube size used, as shown on the diagram’s below.
These clusters shall have two rubber bands wrapped around them to keep them together, and will be placed in a beaker to prevent them from falling over. Once set up they will be filled with water heated to 50 degrees centigrade (heated using a Bunsen burner) and then put into their relevant beakers. This is to make it a fair test as any water that spills over could affect the experiment. Thermometers will then be put into the test tubes (1 in each layer), and the results they show written down every 30 seconds for ten minutes. Each experiment shall be repeated three times, and the average of each try recorded.
It is also important to note the safety considerations of this procedure. The water temperature (50 degrees) can do no harm to a person, and does not burn or hurt when you touch it. It is heated over a heatproof mat as this decreases the probability of the Bunsen causing a fire, or undesirably lighting anything. Also the test tubes are put in a beaker to reduce the risk of them being dropped and broken, which would be a safety risk as someone could be cut or hurt by such a thing happening.
The results will be recorded to the best of the accuracy allowed by the used thermometer, and I shall be careful to read it accurately to within 0.5 of a degree.
Diagram:
Factors That May Affect The Experiment and How I Will Control Them:
Volume of water in test tubes: 1 cm below full
Temperature of water: 50 degrees centigrade
Results (as averages of each of the three tries) *:
* Unfortunately, due to time constraints, I have only been able to obtain three sets of results (1, 7 and 19 test tubes) as opposed to the five set out in my plan.
Graphs:
Analysis:
Conclusions:
Basically, more layers means the tubes on all levels stay warmer longer. This suggests huddling brings about the same benefits to penguins, demonstrating it as a valid explanation.
The graphs show that as time goes on, the temperature in all the test tubes gradually decreases over time. The rate of temperature decrease itself decreases as time goes on also, forming a curve on the line of best fit. The further out a tube is from the centre, the faster its temperature decreases. Also the more tubes that are in any test tubes ‘cluster’ the slower its temperature will decrease.
These conclusions can be supported by the scientific details described in the hypothesis. First of all, that the test tubes stay warmer longer when grouped together is because: 1) The surface area of the whole group will be lower compared to if all those in the group were standing alone. This reduces the amount of heat evaporated and radiated away. 2) The increased insulation due to of the entire group standing together decreases heat loss again. 3) Lots of the heat radiated away from each one goes into another one, this will be concentrated most on the inside one. This slows down the cooling down of each one; with most of the heat loss (except from those on the very outside) is actually used to warm up another one. The other reason that supports this conclusion is that as the temperatures in which penguins huddle are normally too cold for them to survive on their own for a long period of time, and huddling warms them up, it is reasonable to assume that huddling increases their chances of survival, which is a valid reason in itself.
This fits in well with my prediction, as they suggest that penguins huddle to keep warm, as demonstrated above. Also my prediction that the temperature of the test tubes would gradually decrease over time and would do so faster when in a bigger cluster.
Evaluation:
The evidence obtained was reasonably accurate, although there was room for improvement in the area of measuring data. This was mainly because the time between measurements was hard to achieve due to the collective time it took to read all of the collective thermometers in the experiment one after another, although I believe this could have been improved. Also important to note is that the values taken were rounded to the nearest 0.5.
The anomalies that are present are not big and therefore rather un-noticeable (considering what was outlined above), although one specific one may be brought to attention, as it is the only main one that is inconsistent with the rest in it’s range, which is one the cluster of seven tubes on the outer layer (circled in red on it’s graph and on the table of results). To improve this I might use electronic thermometers that are easier to read (and more accurate) and also just do basic things like having the stopwatch beep to remind me to take results on time, and to be efficient (e.g. turn thermometers to face me after using them).
I do think though, considering this that the experiment was planned and done well enough anyway, and that it was definite and suitable enough to support my prediction and to draw my conclusion, and in fact it would have had to be a lot worse to be considered unreliable to not draw the same things.
For further work to improve the accuracy of the work I would follow my plan more accurately, doing 5 experiments instead of three. This would further demonstrate the extend of the validity of my conclusion. I would also use electronic thermometers, and use two for each measurement to test for any inaccuracies in the equipment. These two things together would provide me with a much more accurate and reliable set of results, which would even more greatly demonstrate my conclusion!!!
