Understanding the Difference Between Evaporation and Boiling

In summary, molecules escape from a liquid through evaporation and boiling, but boiling occurs when the vapor pressure is equal or greater than the atmospheric pressure, causing more intense and widespread escaping of molecules.
  • #1
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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  • #2
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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What is evaporation?

Evaporation is the process by which a liquid turns into a gas at a temperature below its boiling point. This occurs when the molecules at the surface of the liquid gain enough energy to break free and escape into the air.

What is boiling?

Boiling is the process by which a liquid turns into a gas at its boiling point. This occurs when the temperature of the liquid reaches a point where the vapor pressure of the liquid equals the atmospheric pressure, causing bubbles to form and rise to the surface.

What is the main difference between evaporation and boiling?

The main difference between evaporation and boiling is the temperature at which they occur. Evaporation occurs at a temperature below the boiling point, while boiling occurs at the boiling point. Additionally, evaporation can occur at any point on the surface of the liquid, while boiling only occurs at the surface where bubbles form.

How does the rate of evaporation and boiling differ?

The rate of evaporation is generally slower than the rate of boiling. This is because evaporation only occurs at the surface of the liquid, while boiling occurs throughout the entire liquid. Additionally, the temperature difference between the liquid and the surrounding air is usually smaller in evaporation, leading to a slower rate of evaporation.

What factors affect the rate of evaporation and boiling?

The rate of evaporation and boiling can be affected by factors such as temperature, humidity, surface area, and air flow. Higher temperatures and lower humidity can increase the rate of both processes, while a larger surface area can increase the rate of evaporation. Air flow can also affect the rate of evaporation, as it can remove the water vapor from the surface of the liquid, allowing for more water molecules to escape.

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