The relationship between pressure and vapor pressure is that boiling occurs when the vapor pressure of a liquid equals the external pressure exerted on it.
Here's a breakdown:
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Vapor Pressure: The pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in a closed system.
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External Pressure: The pressure exerted by the surroundings on the liquid. This is often atmospheric pressure, but it can be any applied pressure.
Boiling Point and Pressure
The crucial link between pressure and vapor pressure is best seen at the boiling point:
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Boiling: A phenomenon where bubbles of vapor form within the liquid.
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Boiling Point Definition: According to the reference, when the vapor pressure equals the external pressure, bubbles of vapor form within the liquid, and it boils.
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Normal Boiling Point: The specific temperature at which a substance boils when the external pressure is 1 atmosphere (atm).
How External Pressure Affects Boiling Point
The external pressure influences the boiling point:
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Higher External Pressure: A liquid needs a higher vapor pressure to boil. This is achieved at a higher temperature. Thus, increasing external pressure raises the boiling point.
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Lower External Pressure: A liquid can boil at a lower temperature because the vapor pressure needed to overcome the external pressure is lower. Therefore, decreasing external pressure lowers the boiling point.
