melting ice to find the value of the latent heat capacity of fusion of ice

7/30/2019 Melting ice to find the value of the latent heat capacity of fusion of ice

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Marc Wierzbitzki Physics HL 20 January 2011

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Melting ice to find the value of the latent heat capacity of fusion of ice

Aim:

With the help of this experiment, we wanted to find the value of the latent heat capacity of fusion (Lfus) of

water.

Construction:

Method:

After setting everything up as shown in the illustration above, reset the mass balance to 0 so that the mass

of the beaker and the thermometer will be ignored, because only the mass of the ice and water matter.

Start by filling the water into the big beaker and note down the temperature and mass. After doing that,

also give in the ice and wait until it is completely melted. Note down the additional mass and the final

temperature.

Results:

MI (g) MW(g) T1(I) (C) T2(W) (C) T2(C) MITW (gK) MWTW (gK) E (J)0.2g 0.2g 1C 1C 1C 11% 11% 30%

21.30 150.00 0 53 40.0 0852 -1950 04597

45.90 112.00 0 40 13.0 0597 -3024 10163

50.00 220.00 0 56 36.0 1800 -4400 10886

19.30 164.10 0 65 52.0 1004 -2133 04730

30.50 189.00 0 34 23.0 0702 -2079 05768

41.97 133.87 0 49 18.5 0776 -4083 13845

77.21 133.38 0 44 07.5 0579 -4868 17959

20.08 100.00 0 45 25.5 0512 -1950 06021

07.25 100.00 0 48 40.0 0290 -0800 02135

37.25 100.00 0 42 17.0 0633 -2500 07816

46.16 100.00 0 52 16.0 0739 -3600 11981

04.50 050.45 0 57 46.0 0207 -0555 01457

15.20 050.30 0 60 35.0 0532 -1258 03038

54.20 163.70 0 65 33.0 1785 -5238 1445868.60 163.50 0 67 29.0 1989 -6213 17684

Error analysis:

The smallest error can be found in the masses of water and ice, as the mass balances we used were quite

accurate. Comparing them to each other, the biggest deviation we noticed was 0.2g. The thermometers

all displayed the same temperature, but as they were not digital, we could only read the results with an

error of 1C, whereas a digital thermometer would have been more accurate. Using those values, we

calculated that the error for MITW has to be 11% and for E30%. Those two errors are quite big (as you

can see in the graph below), which will make it harder for us to decide whether our final result is right or

not.


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Graph:

The above graph gives a mean value of Lfus=245.15Jg-1. The minimum value is equal to 147.65 Jg-1, whereas

the maximum value is 305.37 Jg-1. Therefore, we can compute an error to the mean value of 97.5 Jg -1.

Looking at the result that we expected (L fus=334Jg-1), our result still fits into the error range. But on the

other hand, the experiment is still not very conclusive, since the error is about 40% of the mean value and

the range it gives us is simply too big.

The problem with this experiment was probably the amount of energy that was lost to the surroundings.

This happened at two situations throughout the experiment and therefore the total error added up to

30%. Firstly, we assumed that the ice was constantly at 0C, which is not true. While doing the

y = 245.15x + 19.706

y = 305.37x - 293.13

y = 147.65x + 1200.3

0

5000

10000

15000

20000

25000

0 10 20 30 40 50 60 70 80 90

-(CW

(MI

TI+MWTW)

MI

Lfus


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experiment, you could definitely see that more and more ice melted, it was wet as we did not put it back

into a refrigerator after we had used it. Also, since the water was very hot, it constantly loosed mass

through evaporation, which we did not capture. This affected the value of E (shown in the last column in

the table). Improvements to this could lower the error for this value.

Possible ways to improve the experiment:Looking at the problems that I described above, quite many improvements can be suggested. Firstly, since

this is the most significant error source, we have to minimize the energy loss to surroundings. To do so,

we should not use a beaker anymore but utilize a thermos flask, which would eliminate the effect of the

temperature surroundings. Furthermore, we should also think about closing the flask entirely so that no

water can evaporate and disappear, but it would be trapped within the flask.

Also, it has to be ensured that the ice stays at the same temperature throughout the whole experiment,

otherwise no conclusion can be drawn. To make this possible, the ice should be stored in a refrigerator

until it is needed, just like the water should be boiled for each new repetition.

To reduce all other errors as much as possible, a digital thermometer and mass balance should be used.

Those two devices will reduce the errors in the mass and temperature readings since they are more

accurate and no mistakes can be made when reading off the corresponding values.

Redoing the experiment with the improved set-up will hopefully reduce the errors that have beenmentioned above. Since we tried to eliminate the energy loss to surroundings, the results in general

should be more accurate and closer to the actual value of 334Jg-1.

melting ice to find the value of the latent heat capacity of fusion of ice

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