Factors affecting heat loss from the body
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Factors affecting the rate of heat loss from the body I am being asked to carry out a practical investigation which considers the factors affecting heat loss from the body. The aim of this investigation is to look at the effect of size on temperature loss in warm-blooded animals. I am going to discover and learn more about the relationship between objects and the rate at which they loose heat. I will be using beakers in correspondence to animals during this investigation. I will also be applying my knowledge of homeostasis in correlation to what I discover. Homeostasis is the property of either an open system or a closed system, especially a living organism that regulates its internal environment so as to maintain a stable, constant condition. This need for constancy was recognised in the nineteenth century by Claude Bernard. He concluded: 'La fixité du milieu interieur est la condition de la vie libre.'1 Which means: 'The constancy of the internal environment is the condition of the free life.' The temperature of environments inhabited by living organisms ranges from 90°C in hot spring to -40°C in the Arctic. Most organisms, however, live in the narrow range of temperature 10-30°C. To survive, most animals need to exert some control over their body temperature.
6. Immediately record the initial temperatures start the stop watch and secure the tops of each beaker tightly. (Consider elastic bands to secure the insulating cotton wool). 7. Take the temperature every 5minutes and record these. These results will used for analysis. 8. Continue taking the temperature 5 minutes for the next 30 minutes. Hypothesis The addition of insulation will reduce the rate of heat lost. The reason for this is that heat is lost in 4 main ways in these experiments; evapouration, conduction, convection and radiation. By the addition of cotton wool which I am using to simulate the insulation, I am preventing evapouration because the hot air can't escape, and I am preventing convection because there are no currents of air taking away the hot air. I also predict that the rate at which heat is lost will be reduced by more than half because the ways in which heat can be lost is eliminated by the addition of cotton wool as the insulation. Results Time (mins) 0 layers 1 layers 2 layers 3 layers 4 layers Initial 0 84°C 84°C 84°C 84°C 84°C 5 73°C 81°C 81°C 82°C 82°C 10 65°C 78°C 78°C 79°C 80°C 15 59°C 72°C 71°C 75°C 78°C 20 55°C 71°C 73°C 74°C 77°C 25 51°C 70°C 72°C 73°C 75°C 30 48°C 65°C 70°C 71°C 73°C Total temp.
I imagine that the curves would have evened out into a straight line if I had of extended the duration of the experiment showing that heat loss had slowed right down to almost a halt. The beaker with 4 layers of insulation lost only 13% of the initial temperature and the beaker with no insulation lost on average 41% approx. First I obtained the result from taking the two results which I recorded for the 200ml beakers with no insulation and calculated the average. Variable 1 Variable 2 Initial starting temp. 84°C 89°C Total temp. Lost 36°C 42°C % Loss 43 46 So, 36 + 42/ 2 = 39°C total temp, lost. % lost = 43 + 46/2 = 41% I also hypothesised that with the use of cotton wool as an insulator, heat loss should be reduced by more than half. For this I was able calculate the percentage of heat loss that the cotton wool was able to prevent. 1. With 4 layers heat loss = 11°C No layers heat loss = 36°C 25°C difference, so, 25/84 x 100 = 29.8% prevention 2. With layers heat loss = 11°C No layers heat loss = 42°C 31°C difference, so, 31/89 x 100 = 34.8% prevention 3. 29.8 + 34.8/2 = 32.3% prevention from heat loss. It is therefore correct to say that the rate of heat loss decreases with time.
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