Key Terms
- Kinetic particle model: explains properties using particle arrangement and movement
- Change of state: physical change — reversible, no new substance
- Sublimation: solid → gas directly
- Forces of attraction: hold particles together in solids and liquids
Must-Know Facts
- Solid: close, regular, vibrate. Liquid: close, random, flow. Gas: far apart, random, move fast.
- Heating curve plateau: energy breaks forces, not kinetic energy — so T stays constant.
- Stronger forces → higher melting/boiling point
- State symbols: (s) (l) (g) (aq)
- Gas only can be compressed — particles far apart
Key Misconceptions to Avoid
- Steam is NOT hotter than boiling water — same temperature, different energy form
- Temperature stays CONSTANT during melting and boiling
- Liquids have a fixed volume (not gases)
Model Limitation
- No forces of attraction shown
- Particles treated as identical hard spheres
- Ignores internal structure and size differences
Key Equations
- No calculation equations — this topic is descriptive
- Energy supplied at melting/boiling point breaks intermolecular forces (not raises temperature)
- State symbols: (s) = solid, (l) = liquid, (g) = gas, (aq) = aqueous
Common Mistakes
- Saying temperature rises during melting/boiling: Temperature stays constant — energy breaks forces between particles, not kinetic energy
- Saying gas particles move faster when heated (not liquids): All particles move faster when heated; gases just have more freedom of movement
- Thinking liquids are compressible: Only gases can be compressed — liquid and solid particles are already touching
- Forgetting state symbols in equations: Always include (s), (l), (g), or (aq) — marks are lost without them