Investigation to See How Insulation Affects Heat Loss

We are trying to find out how layers of insulation wrapped round a beaker with hot water in will affect the heat loss in five minutes. The are six different variables that we could alter such as amount of water, temp of water, size of beaker, if the beaker has a lid, if the beaker is on a heat proof mat and the temp of the class room (which we cannot control). We are going to vary the layers of insulation from no layers to four, we are also going to do the experiments without a lid and one with but both times the beaker will be placed on a heat proof mat. We are going to use 125ml of hot water in a 300ml beaker. We are going to the experiment twice then get an average measure the heat loss from when the temp has got to 70�C and is not rising any more we will then start the stopwatch. I predict that the insulation may make some difference but once you have got to about four layers it wont prevent any more heat loss, I also think that the lid will make a lot of difference because it reduces convection allot.

Equipment

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Two 300ml beakers

Two thermometers

A heat proof mat

Eight strips of polystyrene insulation

Two polystyrene lids

A kettle or source of water over 80�C

Two stopwatches

Investigation to See How Insulation Affects Heat Loss

Method

We will boil the kettle then pour it in a measuring cylinder to get 125ml then pour it into the beaker, add the thermometer and wait until the temp is at 70�C and not rising then start the timer for five minuets. At five minutes we will take the temperature and work out the heat loss. After that we will repeat the experiment to get an average. To make sure the results are accurate we will measure the water the look at the reading from the same level.

Results

The results were measured from 70�C and we measured the heat loss.

Results for experiment without lid.

No insulation

1 layer

2 layers

3 layers

4 layers

1st

11�C

11�C

9�C

9�C

8�C

2nd

11�C

9�C

8�C

101/2�C

9�C

Average

11�C

10�C

81/2�C

93/4�C

81/2�C

Results for experiment with lid.

No insulation

1 layer

2 layers

3 layers

4 layers

1st

6�C

5�C

4�C

4�C

4�C

2nd

8�C

6�C

5�C

4�C

2�C

Average

7�C

51/2�C

41/2�C

4�C

3�C

I have highlighted two results that seemed slightly out of sequence. These results seemed out of sequence because the results had steadily declined then the temperature jumps up by 21/2 �C from 8�C to 101/2�C so that affected the average.

Investigation to See How Insulation Affects Heat Loss

Conclusions

The first graph had one odd result, which was experiment two insulation three. The result was 101/2�C which kind off made its line and the averages line on the graph look out of place. On the whole the graph slowly drops then at three layers of insulation shoots up by about two degrees it then starts declining again. The second graph, which had a lid, declines steadily and there doesn’t seem to have any odd results.

The first set of experiments (without lids) lost a lot of heat through convection because there is a lot of hot water exposed to the cooler air. The cooler air heats up and then rises drawing in more cool air to the hot water, which is giving of lots of energy heating the cool air that keeps circulating until the hot water is cool. The second set of experiments (with lid) lost quite a lot of heat at the beginning when there wasn’t much insulation but once it got to about two layers the water was only losing about 4�C . At the begging the water was losing quite a lot of heat through convecion and radiation but as the layers built up the heat loss got suprisingly low, in one case only a loss of 2�C.

My predicion was roughly accurate with the idea about the lid making a lot of difference and the insulation not making much difference.

Investigation to See How Insulation Affects Heat Loss

Evaluation

My results were not very accurate on the first graph but they improved on the second graph. There was one odd result which I cannot explain but it may have been something to do with classroom temperature or a missread thermometer. We had two problems with our method which were, when you poured the water in to the beaker you had to wait for the temerature to drop to 70�C before you could start the stopwatch another problem was that we couldn’t get the lid to sit properly on the beaker. We started the experiment only intending to mesure the temperatur difference for without a lid, but then dicided to do the experiment with the lid aswell so we could see how much convection made a difference.

If I were to do the experiment again I would do the amount of insulation to eight to see where it stoped making a difference I would also try to measure out the hot water more acurately, also I would start the stopwatch at 80�C.