Volatility

Volatility is the physical property that describes the tendency and ease with which a substance vaporizes into a gas or vapor at normal temperatures and pressures ¹.

Volatility and Evaporation

While evaporation is the surface process of turning from liquid into gas, volatility is the intrinsic substance property determining how rapidly this process takes place ²:

• High Volatility: Rapid evaporation rate at room temperature (e.g. ethanol, propanone) ¹.
• Low Volatility: Slow evaporation rate at room temperature (e.g. water, glycerol) ¹.

Key Physical Determinants

Volatility is governed by three interrelated thermodynamic and kinetic factors ²:

1. Intermolecular Forces: Inversely proportional. Weaker attractions between molecules allow surface particles to escape more easily, raising volatility ¹.
2. Boiling Point: Inversely proportional. Substances with low boiling points require less energy to overcome attractions, exhibiting high volatility ².
3. Vapor Pressure: Directly proportional. High volatility correlates with high equilibrium vapor pressure at a given temperature ².

Weak Intermolecular Forces
          |
          v
  Low Boiling Point  <=======>  High Volatility  <=======>  Rapid Evaporation
          |                                                       |
          v                                                       v
High Vapor Pressure                                      Fast Cooling Effect

Practical Significance

• Distillation: Differences in volatility enable separation of liquid mixtures (e.g. crude oil fractional distillation) ¹.
• Safety: Highly volatile liquids generate flammable vapor-air mixtures easily at room temperature ¹.

Related

• Volatile - Substances that evaporate rapidly at room temperature.
• Evaporation - Surface liquid-to-gas transition below boiling point.
• Boiling - Bulk phase transition occurring at a fixed boiling point.
• State of Matter - Macroscopic physical forms of matter.
• Chemistry - Core science area.