gases – particles in continuous random motion; negligible attractive forces; pressure from wall collisions; average kinetic energy ∝ Kelvin temperature; all gases same KE at same T.
liquids – particles close, move in all directions (translational, rotational, vibrational); inter-particle forces give fixed volume & level, but no fixed shape.
solids – strong inter-particle forces; fixed positions; particles only vibrate (no translation/rotation); fixed shape & volume.
plasma – mentioned as fourth state, but focus on kinetic theory: particles ionized, high energy.
“collisions without loss/gain of energy; no friction; same chemical nature across states (e.g., water).”
Gas: free motion, negligible forces. Random & straight till collision.
inter-particle forces: Liquid – close, moving, all three motions. Pressure = collisions with walls.
Vibration only in Solid. “No TRV” (translation+rotation vanish in solid).
➡️ average KE ∝ T(Kelvin) — same for all gases at same T.
🌀 three states same chemical nature — water example.
starter (5m): ask “why gas fills container?” — elicit particle ideas.
introduce (10m): kinetic postulates: motion, forces, temperature.
guided (10m): compare solids/liquids/gases using ball & ring demo (or mimic).
activity (10m): students act as particles (gas: run, liquid: close walking, solid: vibration).
plenary (5m): quick q&a, connect to water example.
• “particle model race”: three groups (solid/liquid/gas) show movement.
• each student gets a label (translational, rotational, vibrational) and must join correct state.
• draw particle arrangements on mini whiteboards.
• discuss why pressure constant at steady temp (elastic collisions).
✓ particles always in motion; higher temp = faster KE.
✓ gas particles have weakest forces, solid strongest.
✓ same substance (water) can be all three – physical change only.
✓ remember: vibrational in all states? yes — even gas molecules vibrate (but also translate/rotate).