01Particle view
Solids: fixed positions, vibrate. Liquids: close but slide past. Gases: far apart, fast, random. Phase is a tug-of-war between IMFs and kinetic energy.
Higher temperature = more KE = particles escape attractions.
02Notebook box
Vapor pressure ↑ when IMFs ↓ or T ↑. Boiling: vapor pressure = external pressure.
Worked example: Water boils at lower T on a mountain because external pressure is lower.