Measuring specific latent heat of vaporization of water
Measuring Specific Latent Heat of Vaporization of
Water
Introduction:
The aim of this experiment was to determine the specific
latent heat of vaporization of a liquid using basic equipment and calculations.
The accepted value of the latent vaporization heat is 2.3x 104 Jkg-1.
Hopefully the results obtained will be similar to the accepted value.
Apparatus:
Kettle
3 beam Scales
Stop watch
Variables:
Method:
1.
Take the kettle and fill it up half way
with water
2.
Put it on the scales and measure the
mass
3.
Record the mass in the data table
4.
Turn on the kettle
5.
When the water starts to boil start
timing
6.
Stop timing when 50 grams of water have
been lost
7.
Record in the data table
8.
Repeat steps 1-7 five times
Data Collection and Analysis
Time of the trials
|
Trials
|
Time/s
± 5s
|
|
1
|
0.050
|
187
|
|
2
|
0.050
|
180.0
|
|
3
|
0.050
|
180.0
|
|
4
|
0.050
|
192
|
|
5
|
0.050
|
145
|
|
Average
|
0.050
|
186
|
Uncertainties
Pt=mLv 
Trial 1 m=0.05 t=187s
Trial 2 m=0.05 t=180s
Trial 3 m=0.05g t=180s
Trial4 m=0.05kg t=192s
Trial 5 m=0.05kg t=189s
Average
|
Trials
|
1
|
2
|
4
|
5
|
|
Lv
/Jkg-1
|
2.7
x 106
±349110
|
2.6
x 106
±338688
|
2.8
x 106
±355622
|
2.6
x 106
±338688
|
2.1
x 106
±237300
|
Conclusions and evaluations
The calculated value of the specific latent heat of
vaporization was supposed to be 2.3 x 106 J/Kg. Unfortunately the
results achieved by the calculations were not perfect and did not reach the
accepted values. All the Lv calculated were in one range, but did
not come close to 2.3 x 106.
The median value of the calculated Latent heat of
vaporization was modelled by the equation
y= 25520x+2657760
The reasons of such weak results were the
uncertainties of the procedure, and old equipment. The scientist didn’t have a
set time to start timing the boiling water, therefore the time could be the
reason of the misleading calculations. The scales that the scientist was
usingwere three-beam, and not electronic. This could as well be a reason of the
uncertain mass. It was difficult for the scientst to measure the exact
moment,when the water had evaporated 50 grams of water.
Reasonable improvements for this experiment would
be, setting a time for the scientist to start measuring