In this experiment, I will test different types of material and how they affect heat loss from the body. The materials I will use are; wool, cotton wool, cotton, felt, foam, polystyrene and newspaper.
As it is difficult to accurately measure which materials stop heat loss from the body, I will instead measure heat loss from a conical flask. I will be testing which material insulates the best, and I will keep all the other variables constant. As 36.9ï¿½C is quite a low temperature I will use a higher one, 80ï¿½C, to test each material. The amount of water, as well as the starting temperature will be kept constant throughout; as will the size and shape of the conical flask. There will be a beaker around the conical flask, holding the insulator, so this test is on a constant volume, rather than mass of insulator. There will also be another flask with no insulator, but with all other variables constant.
I predict that, at first, heat loss will be slow, as the glass of the conical flask will insulate the water; however, this is the same for all materials and should not affect the results. I also predict that foam will be the best insulator.
I am varying the type of material and in general materials with more air gaps will be better because they trap a layer of air and thus insulate. However, bigger air gaps are not necessarily better because the air has the energy to move. This is convection: hot air will rise and thus escape unless it is trapped. This is how the hairs on our skin work. They trap a layer of heat by standing up when we are cold. Humans, however, are not very good at insulating because we have very short hairs and convection currents take the heat away. This is why we wear clothes. Clothes are very good at trapping a layer of air because it is very hard for the air to move away.
The reason air insulates is because it is a gas and a) has no free moving electrons and b) its atoms are spread far so it is harder for the heat to radiate.
Each material has a different structure and this depends on whether it will insulate or not. For example:
Wool has an almost honeycomb structure but these air gaps could be too big so the air will escape.
Convection occurs because the air around is heated by the water and becomes less dense and therefore rises. The bung in the top of the flask stops this to a certain extent, however, large air spaces allow convection. Foam, when packed properly, has none of these and should be a good insulator.
Radiation occurs through the foam, however, some may be reflected by the white, shiny colour, which best prevents against radiation.
In the experiment, after the glass has been heated, the insulator will allow quite rapid heat loss as the insulator and air pockets are warmed. This will result in a slight fluctuation in loss in the first few minutes of the experiment. After the insulators have been heated, loss will slow, causing a graph of heat loss against time to look like so:
Whereas a flask with no insulator may look like this:
I predict wool will be the worst insulator as it has large air pockets allowing conduction and convection to occur. It also has little substance to absorb heat.
It is important to ensure that long hair is tied back, jackets are not worn, ties and shirts are tucked in, stools and benches are underneath tables to prevent accidents with boiling water. Care must be taken when handling and measuring the water and gloves should be warn to prevent against the burning of hands. Sensible behaviour should be present at all times.
In the experiment I will use; a conical flask, beakers, a kettle, water, a thermometer, a stopwatch and the materials mentioned above.
1. Boil water with a kettle, measure out 200cmï¿½ of this water.
2. Add it to a conical flask that is sat in a beaker and surrounded by one of the insulating materials, as shown above.
3. Record the initial temperature and the temperature at one-minute intervals for twenty minutes thereafter.
4. Repeat the steps 1-3 for each insulating material, (including with no material at all – this is the control).
5. Repeat the whole experiment 3 times to eliminate experimental error as much as is possible, and to give a number of readings to take an average from, giving a more accurate set of results.