Sublimation

Definition

Sublimation is the phase change where a substance transitions directly from a solid to a gas without passing through the liquid state. It occurs when the molecules in the solid phase gain enough energy to overcome intermolecular forces and enter the gas phase.

5 Must Know Facts For Your Next Test

1. Sublimation occurs at temperatures and pressures below a substance's triple point in its phase diagram.
2. Common examples of substances that undergo sublimation include dry ice (solid CO2) and iodine.
3. The enthalpy change associated with sublimation is called the enthalpy of sublimation, which can be calculated using Hess's law: $\Delta H_{sublimation} = \Delta H_{fusion} + \Delta H_{vaporization}$.
4. Sublimation is an endothermic process, meaning it requires an input of energy for the phase transition to occur.
5. In thermodynamics, sublimation can be described using the Clausius-Clapeyron equation, which relates the pressure and temperature during phase changes.

Review Questions

• What conditions (temperature and pressure) are necessary for sublimation to occur?
• How can you calculate the enthalpy of sublimation using Hess's law?
• Why is sublimation considered an endothermic process?

Related terms

Triple Point:

The unique set of conditions at which all three phases (solid, liquid, and gas) of a substance coexist in equilibrium.

Clausius-Clapeyron Equation: A formula that describes the relationship between vapor pressure and temperature during phase transitions.

Enthalpy of Vaporization: The amount of energy required to convert a liquid into a gas at constant pressure and temperature.