• Solid (s) ------ Liquid (l) --------- Gas (g)– Phases: ‘physical state’

• Solids– Definite volume and shape

• Liquids– Definite volume, but form determined by container it is in

• Gases– No definite volume or shape

• Solids– Strong attraction between molecules- fixed position (vibrate)– Heat breaks fixed arrangement

• Liquids– Molecules ‘flow’

• Gases – Heat causes attractions between individual molecules to be

broken– Move in random manner– Bump into the container – ‘pressure’

• Gas molecules continue to move and bump into each other

• Move from higher concentration areas to lower areas of concentration

• Occurs in: – Gases, liquids

• Diffusion Animation

• Animation

• Molecules are heated below the surface, gain kinetic energy and bump into molecules at the surface

• Surface molecules are released (attraction to other molecules broken)• Why is this a cooling process?

– The slower moving molecules left behind (lower temperature) cools the air or body (perspiration)

• This is a warming process

• Why?

• Gas particles cool and reach the surface. Kinetic energy absorbed by surface molecules. Molecules form attractions– This increases temperature

• Physical change: a change in the physical properties of a substance.

• Chemical change: the transformation of one or more substances into others.

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