1. Chemistry 17.3

2. What does the Heat Capacity of an object depend on?

3. Heats of Fusion and Solidification
17.3
Heats of Fusion and Solidification
The quantity of heat absorbed by a melting solid is exactly the same as the quantity of heat released when the liquid solidifies; that is, ∆Hfus = –∆Hsolid.

4. Heats of Fusion and Solidification
17.3
Heats of Fusion and Solidification
The molar heat of fusion (∆Hfus) is the heat absorbed by one mole of a solid substance as it melts to a liquid at a constant temperature.
The molar heat of solidification (∆Hsolid) is the heat lost when one mole of a liquid solidifies at a constant temperature.

5. 17.4

6. 17.4

7. 17.4

8. 17.4

9. for Sample Problem 17.4
Problem Solving Solve Problem 21 with the help of an interactive guide tutorial.

10. Heats of Vaporization and Condensation
17.3
Heats of Vaporization and Condensation
The amount of heat necessary to vaporize one mole of a given liquid is called its molar heat of vaporization (∆Hvap).
The amount of heat released when 1 mol of vapor condenses at the normal boiling point is called its molar heat of condensation (∆Hcond).

11. Heats of Vaporization and Condensation
17.3
Heats of Vaporization and Condensation
The quantity of heat absorbed by a vaporizing liquid is exactly the same as the quantity of heat released when the vapor condenses; that is, ∆Hvap = –∆Hcond.

12. Heats of Vaporization and Condensation
17.3
Heats of Vaporization and Condensation

13. 17.5

14. 17.5

15. 17.5

16. 17.5

17. for Sample Problem 17.5
Problem-Solving Solve Problem 24 with the help of an interactive guided tutorial.

18. 17.3
Heat of Solution
During the formation of a solution, heat is either released or absorbed.
The enthalpy change caused by dissolution of one mole of substance is the molar heat of solution (∆Hsoln).

19. 17.3
Heat of Solution
When ammonium nitrate crystals and water mix inside the cold pack, heat is absorbed as the crystals dissolve.
The cold pack shown has two sealed plastic bags, one inside the other. The outer bag contains ammonium nitrate crystals. The inner bag contains liquid water. When the pack is squeezed, the inner bag breaks, allowing the ammonium nitrate and water to mix. Inferring How would you define the system and the surroundings in this process?

20. 17.6

21. 17.6

22. 17.6

23. 17.6

24. for Sample Problem 17.6
Problem-Solving Solve Problem 26 with the help of an interactive guided tutorial.

25. 17.3 Section Quiz.
17.3.

26. 17.3 Section Quiz.
1. The molar heat of condensation of a substance is the same, in magnitude, as its molar heat of
formation.
fusion.
solidification.
vaporization.

27. may increase or decrease. increases. decreases.
17.3 Section Quiz
2. The heat of condensation of ethanol (C2H5OH) is 43.5 kJ/mol. As C2H5OH condenses, the temperature of the surroundings
stays the same.
may increase or decrease.
increases.
decreases.

28. 17.3 Section Quiz
3. Calculate the amount of heat absorbed to liquefy 15.0 g of methanol (CH3OH) at its melting point. The molar heat of fusion for methanol is 3.16 kJ/mol.
1.48 kJ
47.4 kJ
1.52  103 kJ
4.75 kJ

29. 17.3 Section Quiz
4. How much heat (in kJ) is released when 50 g of NH4NO3(s), moles, are dissolved in water?  ssoln = 25.7 kJ/mol
12.85 kJ
13.1 kJ
25.7 kJ
1285 kJ

30. END OF SHOW