Knowledge Organiser: States of Matter
Key Terms
- Internal energy: total KE + PE of particles
- Melting point: solid → liquid transition temperature
- Boiling point: liquid → gas transition temperature
- Latent heat: energy for state change at constant temperature
- Sublimation: solid → gas (skips liquid)
Particle Properties by State
- Solid: fixed lattice, vibrate only, strong forces
- Liquid: close, disordered, flow past each other
- Gas: far apart, random fast motion, negligible forces
State Changes
- Energy IN (bonds break): melting, boiling, sublimation
- Energy OUT (bonds form): freezing, condensing, deposition
- Temperature CONSTANT during state change
- KE constant; PE changes during state change
Exam Tips
- Flat heating curve = state change (bond breaking)
- Always link flat section to KE/PE distinction
- Mass is conserved during all state changes
- Evaporation ≠ boiling (surface vs bulk)
Key Equations
- ΔE = m × c × ΔT (heating/cooling within a state)
- ΔE = m × L (energy during state change, no temp change)
- During state change: temperature stays constant
- Density: ρ = m ÷ V (gases much less dense than solids/liquids)
Common Mistakes
- Saying temperature rises during a state change: During melting or boiling, temperature stays constant — energy breaks intermolecular bonds, not increase kinetic energy
- Confusing evaporation and boiling: Evaporation occurs at the surface at any temperature; boiling occurs throughout the liquid at the boiling point
- Saying particles are destroyed in gas state: Particles are the same in all states — only their arrangement, movement, and energy change
- Forgetting PE increases during state change: At the flat section of a heating curve, KE stays constant (temperature unchanged) but PE increases as bonds break
- Confusing condensation and precipitation: Condensation is gas → liquid (state change); it is not the same as rain forming in the atmosphere
Memory Aid
- Melting (solid → liquid, energy IN)
- Boiling/evaporation (liquid → gas, energy IN)
- Sublimation (solid → gas, energy IN)
- Condensation (gas → liquid, energy OUT)
- E... wait — reverse: Freezing (liquid → solid, energy OUT)
- Deposition (gas → solid, energy OUT)