The final type of heat transfer that I shall explain about is Radiation. Radiation is very different from the other two types of heat transfers. In radiation, no particles are involved and its transfers its heat energy by waves. These waves travel through a vacuum, this is the only way that the sun’s heat can reach us. Every object emits and absorbs energy in the form of radiation. Hot objects emit more heat radiation than colder objects. Whereas colder objects absorb more heat radiation than hotter objects. Radiation, unlike conduction and convection, depends strongly on surface colour and texture. Darker matt surfaces absorb heat radiation. At the same time, they emit much more heat radiation. This is the opposite with silvered or shiny surfaces. These surfaces reflect nearly all the heat radiation that falls upon them. That is why we are encouraged to wear lighter shades of colour in hot weather.
Prediction:
Based on my research I predict that bubblewrap will be the best insulator. I think this because bubblewrap contains air particles in little pockets of plastic. The particles in air are very far apart from each other and so do not pass on their heat energy to neighbouring particles very quickly. Therefore, the heat will not be able to escape that quickly because of this. This means that this will reduce the amount of conducted heat given off and because of this convection cannot occur. I also think that paper will be the worst insulator. This is because paper is very thin and cannot trap air particles so will give off heat. So heat can be conducted through the paper and therefore it will not reduce the amount of heat lost to the surroundings.
Plan of experiment:
Diagram:
Apparatus:
- Stopwatch
- Thermometer
- Four different materials (cloth, paper, bubblewrap, cardboard)
- Beaker
- Kettle
- Water
- Measuring cylinder (100 cm³)
- Cardboard lid
- Cello tape
Method:
- Firstly, insulate the beaker with cloth.
- Make a cardboard lid to cover the top of the beaker.
- Next, boil the water in the kettle. Then measure 100 cm³ of water and place into the beaker.
- As soon as the temperature reaches, 75˚C start the stopwatch and place the lid on top of the beaker.
- After every minute for seven minutes, measure the temperature and record. Measure the temperatures to the nearest whole number.
- Repeat the experiment again.
- After that change the insulating material and repeat each experiment twice.
Safety:
In order to carry out a good experiment I also have to make sure that the experiment is safe. As safety precautions, I shall do the following:
- I will wear goggles
- I will work away from sockets and electricity mains.
- I will wipe up any spilt water.
- I will be careful when handling boiling water.
Fair test:
Another thing I have to make sure is that to get good results I have to carry out a fair test. To do this I will do the following:
- Use equal amounts of water each time.
- Carry out the experiment for the same amount of time.
- I will make sure that the starting temperature of the experiment is the same each time.
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I will use the same beaker.
Results:
When I was working out the averages to each temperature for each material’s experiment, I rounded the values to the nearest whole number so that it was easier for me to plot the graph.
Different types of insulation used for heat loss reduction
Conclusion:
As you can see from my graph, there are four lines of best fit for the four different materials that I used. All the graph lines are curved. The gradient goes downwards and so they are negative slopes. As the time at the x-axis increases the temperature of the water in the beakers for the different insulations decreases. This is because the temperatures were cooling as they were losing heat to the surroundings.
The line of best fit for paper has the steepest gradient and has the greatest temperature decrease. Therefore, when paper was used as the insulation, a lot of heat was lost to the surroundings. This was because paper gave out heat by conduction. The paper was thin and unable to trap air particles in between the solid particles of the paper. As paper is solid and solids are good conductors of heat when the particles vibrated, they passed their heat to neighbouring particles. So therefore, the heat was given out, as paper was not a very good insulator.
The line with gentlest gradient was bubblewrap. The temperature difference was the lowest and the gradient is small. This is because bubblewrap was the poorest conductor of the four materials and so the best insulator of all. This is because the bubblewrap has pockets of air in between the material. Air is a very poor conductor of heat as the particles in a gas are so far apart. This meant the particles from the water passed its energy to the air particles but these particles trapped these warm particles. This reduced the amount of heat lost to the surroundings by conduction and convection currents.
I was surprised to find out that cardboard insulation was not very good at conducting heat and was nearly just as good an insulator that bubblewrap was. I thought cardboard being made of layers of paper meant it would not reduce conduction very well. I was wrong because my results show this. The reason why cardboard was quite a good insulator was because in between the layers there are “gaps.” These gaps were filled with air so in a way these gaps behaved like the pockets of air of the bubblewrap. Again, these gas particles trapped the warmer particles reducing conduction and convection currents from letting out too much heat to the surroundings.
In my prediction, I predicted that bubblewrap would be the best insulator and that paper would be the worst insulator or best conductor of heat from the four materials used. I predicted correctly as my graph shows and my table of results shows.
Evaluation:
If you look at my graph there are four lines of best fits, which are accurate. I can tell this because to each graph line the points are on the line or more or less near the lines. I think this was because I followed my method and I clearly knew what to do.
However, for the lines of best fit for Cardboard the average temperature at 7 minutes and the same with the Cloth graph line there is an anomalous result. I think this may be because of quite a few reasons. Firstly, I think that I did not repeat my experiment more than twice this meant that my readings were not as accurate as they could have been. In future, I should repeat the experiment at least three times for accuracy.
Also the other reason could be that I may have misread the thermometer whilst recording results. Also when I measured the temperatures I removed the lids from the beakers. This meant that some heat could have been lost to the surroundings. I think that I could improve this by making a lid with a hole in the middle for the thermometer so the thermometer would be placed in the beaker for the whole experiment. This would reduce the amount of heat lost.
Also, I started the temperature at quite a low temperature I think that if I started it at a higher temperature I would have been able to record better results and see greater differences between the different insulating materials reduction of heat loss.
Finally, I think that one of the main reasons that I did not have extremely accurate results was because I did not take enough readings. All in all, I just took seven readings so I was unable to make very good judgements. If in future I was to do this experiment I would let the experiment continue for at least ten minutes.
Overall, the experiment went well.
Resources used:
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- bitesize physics
- CGP Revision guide