Topic: Vapor Pressure

Boiling vs. Evaporation occurs at surface of liquid (or solid) occurs at all T liquid cools off as evaporates spontaneous all the time BOILING occurs throughout liquid occurs at definite T occurs at constant T only spontaneous when VP = external pressure

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Vapor Vapor is the gas phase of substance that is normally liquid at room temperature Some evaporation occurs at all temperatures (like you saw with the ice cube) The easier a substance evaporates, the weaker the forces between it’s molecules

Vapor Pressure Pressure exerted by vapor over its liquid VP is affected by temperature: higher the T, higher the VP

Vapor Pressure VP does NOT depend on how much liquid is present VP depends only on temperature

Boiling Point Temperature at which: VP liquid = external atmospheric Pressure Normal Boiling Point: temp at which VP liquid = 1 atm 1 atm = standard atmospheric pressure (what we are feeling here in NY)

all liquids: as T ↑ the VP ↑ Boiling Point

> < Boiling and Pressure If increase external pressure (ex: camping in Death Valley), boiling point is ____ than 100oC If decrease external pressure (ex: eating Raman noodles at top of Mt. Whitney), the boiling point is ____ than 100oC > <