PASCO TD-8557 Basic Calorimetry Set - Manual (Page 11)

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B a s i c C a l o r i m e t r y S e t
9
IMPORTANT: Always remove the steam tube from the water before turning off the steam generator
heat. (Can you explain why?)
9. Immediately determine M
final
, the mass of calorimeter plus water plus (condensed)
steam.
Data
T
rm
= ____________
M
cal
= ____________
T
initial
= ____________
M
cal + water
= ___________
T
final
= ____________
M
final
= ____________
Calculations
When steam condenses in cool water, heat energy is released into the water in two ways.
First, the latent heat of vaporization is released. With this release of heat, the steam is con-
verted into water, but the newly converted water is still at boiling temperature, 100° C.
Second, the newly converted water releases heat as it comes into thermal equilibrium with
the cooler water at a final equilibrium temperature, T
final
.
According to the principle of the conservation of energy, the total heat released by the
steam equals the total heat absorbed by the cooler water. Stated mathematically:
(M
steam
)(H
v
) + (M
steam
)(1 cal/g K)(T
steam
- T
final
) = (M
water
)(1 cal/g K)(T
final
- T
initial
)
M
steam
= M
final
- M
cal + water
= __________________
M
water
= M
cal + water
- M
cal
= __________________
T
steam
= 100 °C
H
v
= the latent heat of vaporization per gram of water
Use your data and the above information to determine H
v
.
NOTE: The thermometer also absorbs a certain amount of heat during the experiment. As a good
approximation, assume that the heat capacity of the thermometer is equivalent to that of 1 g of water
(i.e., add 1 g to M
water
the above equation).
H
v
= ____________
Questions
1. Why would an injury caused by 1 g of steam at 100° C do more damage than an in
jury caused by 1 g of water at 100° C?
2. Speculate on how the heat of vaporization might influence climate and weather sys-
tems.
3. In what way does water used to cook food serve as a refrigerant? (Hint: What happens
when the water all boils away?)