1. Specific Latent Heat of Vaporization Practical
Research Purpose:
To Measure the Specific Latent Heat of Vaporization of Water
Data Collection and Processing
Mass of kettle without the lid = 504 ±1 g
Mass of Kettle with water =1242 g ± 1 g
Change in mass before the temperature of the water reached the boiling point = 22 g
± 2g
Power of kettle = 625 W
Temperature of water = 100°C± 2°
Trials Initial Final kettle Mass loss Time elapsed Latent heat of
kettle mass mass (± 2 g) during mass vaporization(J
(± 1 g) (± 1 g) change (± .01s) kg−1)±126425
1 1220. 1170. 50. 252.85 3160000
2 1161 1111 50. 259.36 3242000
3 1111 1061 50. 242.00 3025000
Average Latent Heat of Vaporization of the Three Trials = 3140000 J kg−1±
126425
In trial four the time was recorded each time the mass dropped 10 g.
Initial kettle mass (± 1 g) Final kettle mass (± 1 g) Time elapsed during mass
change (± .01s)
1040 1030 57:42
1030 1020 114:20
1020 1010 163:01
1010 1000 217:14
1000 990 264:24
The raw data was the temperature of the water, the initial mass of the kettle, the
final mass of the kettle, the time elapsed during the mass change, and the power
produced by the kettle.
The processed data is the mass loss and the latent heat of vaporization.

2. Notes on Uncertainties: The mass of the kettle by itself, the mass of the kettle with
water, the initial mass, and the final kettle mass were all measured by a digital scale
that measured to the nearest gram. Therefore, the uncertainties of these values had
to be 1 gram. The mass loss was constantly held at 50 grams, but in order to get the
value 50 grams the final kettle mass was subtracted from the initial kettle mass.
Since, these values were subtracted, the uncertainty of the initial kettle mass (1 g)
and the uncertainty of the final mass (1 g) had to be added together in order to
obtain the uncertainty of the mass loss, which is 2 g. The value on the back of the
kettle was used to determine how many watts the kettle produced, therefore
negating the need for an uncertainty value. The temperature value was not
necessarily measured, but the experiment was started when the water began to boil,
which means that the temperature had to be the boiling point of water, which is
100°C. Assuming that the water may have begun to slightly boil right before
the temperature reached the boiling point, the uncertainty of the temperature
could roughly be around 2 °C, according to this students estimate.
Sample Calculations
To find Mass Loss
Mass loss = initial mass of kettle – final mass of kettle
Mass loss = 1220 g – 1170 g
Mass loss = 50. g
To find Latent Heat of Vaporization
Theory
Energy supplied to test material = Energy received by water and beaker
(P kettle )(t) = m L v
(625) (252.85 ) = 1220 L v
(625) ( 252.85 ) = L v
50.
3160 J g−1 = L v
(3160)(1000) =L v
3160000 J kg−1= L v
Uncertainty calculation for Latent Heat of Vaporization

3. Uncertainty for time is negligible
Uncertainty for mass = 2/50
Uncertainty for mass = 4%
Uncertainty for Power is not needed because it was taken from the apparatus
Uncertainty for Latent Heat = 4%
Uncertainty for Latent Heat = (.04)(3160000)
Uncertainty for Latent Heat = ± 126425 J kg−1
To find Latent Heat using the slope of a Time against Mass graph
Trial four was used to collect the time every time 10 grams of water was lost.
This data was used to plot a time against mass graph.
Slope of the graph =Time
Mass
Slope of the graph = 5.283 sg−1
(P kettle )(t) = L v
m
(slope) (P kettle )= L v
(5.283)(625) = L v
3301 J g−1 = L v
(3301)(1000) = L v
3301000 ± 126425 J kg−1 = L v
Conclusion

4. This project’s purpose was to find the specific latent heat of vaporization of water.
The literature value for the water’s latent heat of vaporization is 2260 kJ kg−1
(2260000 J kg−1). In this experiment, the average of the results of trials 1, 2, and 3
was 3160000 J kg−1and the result yielded by the graph in trial 4 was 3140000 J kg−1,
showing that the experiment was fairly precise. The difference between the answer
yielded by this experiment and the literature value is an astounding 860000 kg−1.
One primaryfactor in causing this difference is thatthe uncertainty was very high (±
126425 J kg−1), but this is somewhat to be expected with such a large answer.Also,
the lid of the kettle was left off the kettle because the kettle with its lid on had too
much mass to be measured by the equipment in the lab. Since the lid was off, heat
could have been lost and dissipated into the air, as well as some of the mass of water
could have been evaporated off. This could definitely explain why the literature
value and the values obtained by this experiment do not match up. This experiment
and its purpose of determining the latent heat of vaporization has many
applications. An example where this applies is cooking. Many times cooks will put a
substance in water in order to increase its boiling point so that they can heat the
water to very high temperature and cook food fast and efficiently without the water
evaporating. By knowing the latent heat of vaporization of water, cooks and chemist
could be able to determine the most efficient substance and smallest amount of that
substance needed to increase water’s latent heat of vaporization, which would allow
them to cook food at very high temperatures. If food is cooked at high temperatures
then, it can be cooked faster making consumers and people happy.
Several errors attributed the inaccuracy of the results of this experiment. One of the
errors that occurred was that the value of the power produced by the kettle was
taken from the label on the back of the kettle, which was 625 watts. The power
produced by the kettle is probably not exactly 625 watts but could be slightly lower
or less than the value printed on the kettle. This would have affected the experiment
by giving it a larger value than it should have been, which is exactly what happened
in this experiment. This problem could be fixed by using an ammeter to measure the
power produced by the kettle. Another error that occurred was that heat was lost
into the atmosphere because the lid of the kettle was not on top of it. Also mass was
lost because some of the water evaporated into the air. This error could have
decreased the result of the latent heat of vaporization because it would have helped
the water to loose mass more quickly, making the time elapsed smaller. To fix this a
mass scale could be found that was large enough to measure the mass of the kettle
and its lid, so that the lid could be placed on top of the kettle and the mass still
recorded. Another way to improve this experiment is to do the method used in Trial
4. Recording the time every time 10 g of mass is loss and plotting a time against
mass graph will help the experiment be more accurate.