Convection: If a temperature difference arises within a liquid or a gas, then fluid motion will almost certainly occur. This transfers heat from one part of the fluid to another.
Radiation: The process of transmitting waves or particles through space, or some medium; or such waves or particles themselves. Waves and particles have many characteristics in common; usually, however, the radiation is predominantly in one form or the other.
Variables: In this investigation there are many variables. I will have to do many things to ensure this is a fair investigation.
Convection: If a temperature difference arises within a liquid or a gas, then fluid motion will almost certainly occur. This transfers heat from one part of the fluid to another.
Radiation: The process of transmitting waves or particles through space, or some medium; or such waves or particles themselves. Waves and particles have many characteristics in common; usually, however, the radiation is predominantly in one form or the other.
Variables: In this investigation there are many variables. I will have to do many things to ensure this is a fair investigation.
- I will change the water each time I complete a set of results and use the same source of water.
- I will use the same copper mug for all experiments.
-
I will heat all water to 80C
- I will work in the same conditions each time.
- I will use the same amount of material each time
- I will use a lid of tin foil each time.
- The mug will have one layer of tin foil around it.
- The mug will be kept away from anything that may speed up the time it takes to cool
Safety precautions: To keep the experiment safe I shall
- Wear goggles at all times due to the danger of hot water
- Wear a thick overall, which can be removed if any hot water is spilled.
- Wear gloves to protect hands from being burnt.
Equipment
1 mug
1 kettle
1 thermometer
1 heat mat
1 water source
1 of each material (5 in total)
1 tin foil lid
Method:In the experiment, I am going to test 5 different materials in order to discover which is the best at insulating heat. We are to test the materials by wrapping them around a mug, which I will fill with 200ml of hot water at 80c and take the temperature every minute for 10 minutes. This will enable me to see the temperature decline clearly. I will repeat this sequence 3 times for each material to make sure it is fair and take a table of averages at the end. I will be using a thermometer to record the temperature, which is accurate to O.5c. The thermometer will be placed through the tin foil lid.
Preliminary Experiment: This is the first of the series in which I used only the mug with a layer of tin foil around it. I used no lid so I could see the effects of convection and then decide on whether to use a lid in the real experiments using materials. In this we tried to use 300ml of water but found it to be impractical so will use only 200ml for the final experiment. Trying to get water at any temperature higher than 80oc was a rush and mistakes can be made in a rush so we will use 80oc in the final experiment. We tried using a data logger with a heat probe and a thermometer.
We discovered cooling was very quick in this way so we will use a lid in the final experiment. We found the data logger to be rather unreliable so will use the thermometer in the real experiment.
Analysis.
Graphs and tables on separate sheet.
Conclusion: The graph shows a trend with all the materials I have tested in that they all show negative correlation. As time goes on (as temperatures are displayed on the graph for every minute), the temperature of the water decreases. The graph shows the steady decline of temperature with the continuance of time over the ten minute testing time.
The poorer insulating materials have steeper declines. The better insulating materials have less steep/ flatter declines. There is a range between the temperatures of the water after the ten minute testing time of 4.5 oC between the best and worst insulating material.
In the early stages of the graph, the points ( of temperatures vs. time ) are all fairly
close together. With the further continuance of time, larger ranges of temperature occur on the graph as aspects such as conduction, convection and radiation play further part in the cooling process. It is these 3 factors which an insulating material must contend with to determine how good it is at insulating heat.
Conduction is the most influential factor of this cooling investigation so the better insulating materials needed to be good at trapping air to insulate heat as air is a poor thermal conductor which explains why felt and coconut on plastic were better insulators than cotton for example because coconut on plastic and felt are both thick materials and made of matted fibres so were able to trap air and insulate the heat well. In theory, the wool should have been best at reducing conduction as it is very thick
and matted but it has square gaps between each strand ofwool where it has been sown together allowing heat to pass through.
The poor insulating materials (Nylon and cotton) are very thin so unable to trap air hence being poor thermal insulating materials.
The graph reflects the influence of conduction as the materials best at reducing it cooled slowest.
Convection occurs through the sides of the mug but mainly through the top of the mug. To prevent this I have used a tin foil lid. This makes it fajr for all tested
materials as they all have convection reduced equally out of the top of the mug
leaving the material to insulate the convection occurring through the sides.
Radiation can be absorbed or reflected by opaque surfaces and dull rough surfaces absorb more heat. This is much like the properties of coconut on plastic which is why it was good at insulating radiation because its outer plastic could absorb radiation and the dull and rough inside coconut could also absorb heat. This is another reason why it performed best.
