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Unformatted text preview: mLv = (10 g) (2270 J/g) = 22700 J
C. Gas Phase
Unlike a solid or a liquid, a gas completely fills its container, and its volume is drastically changed by temperature and pressure changes. On the average, gaseous molecules are many times farther apart from each
other than molecules of solids and liquids.
To change the temperature of a gas, heat energy must be added. The amount of heat energy that changes
the temperature of 1.0 g of a gas by 1.0°C is called its specific heat (c). Each substance has its own specific heat. The specific heat of steam is 2.02 Joules/g°C. In other words we must supply 1.0 gram of
steam with 2.02 Joules of heat energy to raise its temperature by 1.0 °C.
The general equation for calculating heat energy to change the temperature of a vapor is:
Heat = Mass x Specific Heat (vapor) x Temperature Change
Q = m c DT
H2O(s) at -20°C 10 g B-C
H2O(s) at 0 °C 10 g C-D
H2O(l) at 0°C 10 g D-E
H2O(l) at 100°C 10 g E-F
H2O(g) at 100°C H2O(g) at 140°C 10 g 10 g Calculate the heat necessary to change 10 g of H2O(g) at 100 °C to 10 g of H2O(g) at 140°C....
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This document was uploaded on 01/20/2014.
- Winter '14