Understanding the Difference Between Evaporation and Boiling

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SUMMARY

Evaporation and boiling are distinct processes involving the escape of molecules from a liquid. Evaporation occurs continuously at any temperature, regardless of vapor pressure, while boiling happens when vapor pressure equals or exceeds atmospheric pressure. During boiling, the high vapor pressure allows molecules to escape from both the surface and within the liquid, forming bubbles. The fundamental mechanism of molecular escape is identical in both cases.

PREREQUISITES
  • Understanding of basic thermodynamics
  • Familiarity with the concepts of vapor pressure
  • Knowledge of molecular behavior in liquids
  • Basic principles of phase transitions
NEXT STEPS
  • Research the relationship between temperature and vapor pressure in liquids
  • Explore the concept of phase transitions in detail
  • Learn about the kinetic molecular theory of gases and liquids
  • Investigate the effects of atmospheric pressure on boiling points
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Students in chemistry or physics, educators explaining phase changes, and anyone interested in the fundamental principles of thermodynamics.

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Hello,

This is basic stuff and I feel a bit embarrassed for asking this, but here goes: From what I think I know, evaporation is always happening in a liquid (water, for example) irrespective of the vapor pressure, but boiling only occurs when the vapor pressure is equal or greater than the atmospheric pressure. My question is, how can the molecules escape from the liquid in the former case (evaporation) but are unable to do so in the latter (boiling) until the vapor pressure equals atmospheric pressure?

Thanks!
 
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Molecules escape in both cases and it is exactly the same mechanism. The only difference is that during boiling vapor pressure is so high molecules escape the liquid not only on the surface, but even in the bulk, creating bubbles.
 
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