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General Chemistry Principles, Patterns, and Applications, 2011

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4. The formation of frost on a surface is an example of deposition, which is the reverse of sublimation. The<br />

change in enthalpy for deposition is equal in magnitude, but opposite in sign, to ΔH sub , which is a positive<br />

number: ΔH sub = ΔH fus + ΔH vap .<br />

5.<br />

6.<br />

a. liquid + heat → vapor: endothermic<br />

b. liquid → solid + heat: exothermic<br />

c. gas → liquid + heat: exothermic<br />

d. solid + heat → vapor: endothermic<br />

7.<br />

8. The enthalpy of vaporization is larger than the enthalpy of fusion because vaporization requires the addition<br />

of enough energy to disrupt all intermolecular interactions <strong>and</strong> create a gas in which the molecules move<br />

essentially independently. In contrast, fusion requires much less energy, because the intermolecular<br />

interactions in a liquid <strong>and</strong> a solid are similar in magnitude in all condensed phases. Fusion requires only<br />

Saylor URL: http://www.saylor.org/books<br />

Saylor.org<br />

1037

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