Question

part b: understanding concepts

1. fill in the table below with what happens to temperature, particle motion, and energy transfer when matter changes state.

change of state
solid - liquid (melting)
liquid - gas (evaporation)
gas - liquid (condensation)
liquid - solid (freezing)
temperatu re change
particle motion change
energy flow (heat added or removed?)

Explanation:

• Solid - Liquid (melting): Temperature remains constant (at melting point). Particles gain energy, move more freely (break some intermolecular forces). Heat is added to overcome forces holding particles in solid lattice.
• Liquid - Gas (evaporation): Temperature can vary (but at boiling point it's constant for pure substances). Particles gain enough energy to escape liquid phase (move randomly and freely). Heat is added to provide energy for particles to overcome intermolecular forces in liquid.
• Gas - Liquid (condensation): Temperature decreases (releases heat). Particles lose energy, move more slowly (intermolecular forces become stronger as they come closer). Heat is removed as particles give up energy to form liquid.
• Liquid - Solid (freezing): Temperature remains constant (at freezing point). Particles lose energy, move less (form ordered solid structure). Heat is removed as particles arrange into solid lattice.

Answer:

Change of State	Temperature Change	Particle Motion Change	Energy Flow (heat added or removed?)
Liquid - Gas (evaporation)	Constant (at boiling point for pure substances) or variable	Particles move randomly and freely (gain energy)	Heat added
Gas - Liquid (condensation)	Decreases	Particles move more slowly (lose energy)	Heat removed
Liquid - Solid (freezing)	Constant (at freezing point)	Particles move less (lose energy)	Heat removed