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Finding the latent heat of fusion

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Introduction

Finding the latent heat of fusion of ice

Introduction

In this experiment, I will attempt to determine the specific heat capacity of fusion of ice.

“The specific heat capacity of a substance is the quantity of energy needed to change the temperature of 1kg of the substance by 1°C.”

But when a certain mass of a substance is change from solid to liquid, provided temperature is constant, it is called specific latent heat of fusion of the substance used. Hence the energy required to melt m kg of ice at 0°C is mLfi.e. Q = mLf

The electrical energy (Q) supplied to the heat in time ‘t’ is equal to VIt Q = VIt.

So, in order to calculate specific heat capacity we need:

• Voltmeter to measure voltage
• Ammeter to measure current
•  Stopwatch to measure the time the ice takes to melt
• Colorimeter to provide heat to melt the ice

Results table

 Minutes/s   ± 2 s Voltage/v    (±0.5v) Current/A   (±0.1A) Mass/g                                                (±0.01g) trial 1 trial 2 trial 3 60 9.5 3.0 4.1 2.0 6.1 120 9.5 3.0 5.5 6.8 15.5 180 9.5 3.0 7.3 13.3 19.5 240 9.5 3.0 9.3 18.8 22.7 300 9.5 3.0 12.9 24.9 30.1 360 9.5 3.0 15.9 29.7 42.0 420 9.5 3.0 19.0 33.9 51.6 480 9.5 3.0 24.0 39.7 58.0 540 9.5 3.0 30.1 42.1 62.4 600 9.5 3.0 37.7 50.0 70.0 Observation Voltage: the uncertainty of the voltage used is ±0.5v. This because the scale is to the nearest 1v, thus, I assumed that it would be more accurate to read to the nearest 0.5v than any other reading smaller or larger than 0.5, this unless the measurement marked on the voltmeter. Current: the uncertainty of the current used is ±0.1A. This because the scale on the amnmeter is to the nearest 0.1A. When I took the current reading i could only read to the nearest 0.2A. Hence it would be just to read and take in account an error of 0.1A. Mass: as I was using a 2 d.p. balance, i chose to read to the nearest ±0.01g.

Middle

0.00

60

4.10

4.10

2.00

2.00

6.10

6.10

4.07

2.05

120

5.50

1.40

6.80

4.80

15.50

9.40

5.20

4

180

7.30

1.80

13.30

6.50

19.50

4.00

4.10

2.35

240

9.30

2.00

18.80

5.50

22.70

3.20

3.57

1.75

300

12.90

3.60

24.90

6.10

30.10

7.40

5.70

1.9

360

15.90

3.00

29.70

4.80

42.00

11.90

6.57

4.45

420

19.00

3.10

33.90

4.20

51.60

9.60

5.63

3.25

480

24.00

5.00

39.70

5.80

58.00

6.40

5.73

0.7

540

30.10

6.10

42.10

2.40

62.40

4.40

4.30

1.85

600

37.70

7.60

50.00

7.90

70.00

7.60

7.70

0.15

Uncertainty of  processed average Δmass/g

4.45

Observations:

(Δ g) Run 1: to calculate the change in mass of trial 1 I used the second entry and subtracted by first entry. I repeated this process until the end by subtracting the following value by the preceding.

(Δ g) Run 2: to calculate the change in mass of trial 1 I used the second entry and subtracted by first entry. I repeated this process until the end by subtracting the following value by th preceding

(Δ g) Run 3: to calculate the change in mass of trial 1 I used the second entry and subtracted by first entry. I repeated this process until the end by subtracting the following value by th preceding

Average Δmass /g: to calculate the average change of mass I added all the change of mass values from the trials and divided by 3. And so did that to every single time measured.

Uncertainty of average Δmass/g: to calculate the uncertainty of the change in mass, I took the maximum value of all processed change of mass and subtracted by the minimum value in the same group and then divided by 2. And so did that for the rest of the data processed.

Uncertainty of processed average Δmass/g:

Conclusion

Improvement

The random errors should be looked closely at this experiment. I noticed that I was not consistent in melting the ice. By this I mean that I should have paid close attention when pulling the ice towards the heater. With this done, the amount of ice molten at the top of the funnel would have been the same as the ice molten at the bottom of the funnel keep the melting process consistent.

The apparatus used such as ammeter, voltmeter and stopwatch contributed immensely towards the systematic error. Though, out of the 3 apparatus mentioned above, the stopwatch contributed the most to this part of the error.  I would suggest that the ± 2 would be due to my reaction when stopping the stopwatch. To avoid this type of error I would use the IT system available so that the time at which the experiment should stop is kept constant.

It is worthwhile considering also the voltmeter and the ammeter. This two apparatus are limited to ± 0.5 and ± 0.1 accordingly. It clear that this was a very small error and that would not have affected much the outcome. Though if a more precise apparatus with a larger range was used, then the results would be of a much lower error. This statement was taken from guiding paper.

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