In a similar fashion to melting and freezing, vaporization and condensation are accompanied by energy changes. Answer the following questions to predict what energy transfers occur in these processes.
Worked Example
A fundamental understanding of phase changes is important for understanding the Earth’s climate system.
- By considering the intermolecular forces within a substance, predict whether a substance absorbs or releases energy during vaporization.
- Is vaporization an endothermic or exothermic process?
- During vaporization, a substance absorbs energy. To enter the gas phase, the molecules of a substance must be separated from each other. For this to occur, the intermolecular forces between the molecules must be overcome, which requires the absorption of energy.
- Because energy is absorbed during vaporization, vaporization is an endothermic process.
Your Turn
Predict whether energy is absorbed or released during condensation, by referring to the intermolecular forces within a substance.
During condensation, gas molecules come together to form a liquid. For the molecules to congregate, the intermolecular forces within the substance must be strengthened. The strengthening of intermolecular forces is accompanied by the release of energy. In other words, condensation is an exothermic process.