1. Heat in changes of state
Section 11.3

2. After reading Section 11.3, you should know:
The difference between fusion, solidification, vaporization and condensation
How to calculate the heat changes for each type of reaction

3. Definitions
Molar heat of fusion (∆Hfus) – the heat absorbed by one mole of a substance in melting from a solid to a liquid at constant temperature.
Table 11.5 (pg 308)
Molar heat of solidification (∆Hsolid) – the heat released when one mole of a liquid solidifies at constant temperature.
Determined from Table 11.5 (pg 308)

4. Definitions
Molar heat of vaporization (∆Hvap) – the amount of heat absorbed when one mole of a given liquid is vaporized.
Table 11.5 (pg 308)
Molar heat of condensation (∆Hcond) – the amount of heat released when one mole of a vapor condenses.
Determined from Table 11.5 (pg 308)

5. Definitions
Molar heat of solution (∆Hsoln) – the heat change caused by the dissolution of one mole of a substance; can be absorbed or released.
Molar heat of combustion (ΔHcomb) – heat of reaction for the complete burning of one mole of a substance.
Table 11.4 (pg 305)

6. How they all relate (values on pg 308)
Hsolid and Hfus are opposites
Hsolid = - Hvap
H2O(s) --> H2O(l) Hfus = 6.01 kJ / mol
H2O(l) --> H2O(s) Hsolid = kJ / mol
Hvap and Hcond are opposites, too!
Hvap = - Hcond
H2O(l) --> H2O(g) Hvap = 40.7 kJ / mol
H2O(g) --> H2O(l) Hcond = kJ / mol

7. Heating Curve for Water
∆Hvap
∆Hfus

8. Constants for H20 ∆Hfus = 6.01 kJ/mol ∆Hvap = 40.7 kJ/mol
∆Hsolid = − 6.01 kJ/mol
∆Hcond = −40.7 kJ/mol
Cp (ice) = J/goC
Cp (water) = J/goC
Cp (steam) = J/goC

9. Sample Problem
How many grams of ice at 0oC and kPa could be melted by the addition of 2.25 kJ of heat?
Known Values: Unknowns:
Melting = ∆Hfusion grams of ice = ?
∆Hfusion (H2O) = 6.01 kJ/mol
2.25 kJ of heat are absorbed
? Grams = 2.25 kJ 1 mol grams = grams
6.01 kJ mol

10. After reading Section 11.3, you should know:
The difference between fusion, solidification, vaporization and condensation
How to calculate the heat changes for each type of reaction