The Water Cycle and Energy Transfer
Water changes phase during the water
cycle. Thermal energy is released when
water changes from liquid to a solid.
Thermal energy is absorbed when water
changes from a liquid to a gas.
Heat of Fusion and Heat of Vaporization
Heat of Fusion - The amount of energy absorbed when 1 mol
of the substance changes from solid to liquid, without a
change in temperature. Heat of solidificaton is the same
thing but from a liquid to a solid.
Heat of Vaporization - The amount of energy absorbed when
1 mol of the substance changes from liquid to gas, without a
change in temperature. Heat of condensation is the opposite
of this.
Heating Curve of Water
Calculating the Heat of Fusion and Heat of Vaporization
Q
Hfus =
n
n=
m
M
Hvap=
Q
n
Hfus = Heat of fusion (kJ/mol)
Q = the quantity of thermal energy (kJ)
n = the amount of substance in mol
Hvap = Heat of vaporization (kJ/mol)
m = mass (g)
M = molar mass (g/mol)
Pyramids:
When 27.05kj of thermal energy is added to 4.50 mol of ice
at 0.0ºC, the ice melts completely. What is the experimental
heat of fusion of water?
When 5.00g of ice melts, 1.67kJ of thermal energy is
absorbed. Calculate the experimental heat of fusion of ice.
When 150 g of water changes from liquid to vapour phase,
339kJ of energy is absorbed. Determine the experimental
heat of vaporization of water.
Pags 386 to 387 Practice problems #9 to 15
Page 390 #14 to 21