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Chapter 3. Section 2 Changes of State. I. Changes Between S olid a nd Liquid. Melting – change in phase from a solid to a liquid. 1. Particles move fast enough to break free from their fixed positions. 2. Can be useful in identifying an unknown substance.
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Chapter 3 Section 2 Changes of State
I. Changes Between Solid and Liquid • Melting – change in phase from a solid to a liquid. 1. Particles move fast enough to break free from their fixed positions. 2. Can be useful in identifying an unknown substance. • Freezing – Change in state from liquid to solid. • Particles slow down and get into fixed positions. • Freezing point is the same as melting point.
II. Changes Between Liquid and Gas • Vaporization – phase change where a liquid becomes a gas. • Evaporation – when vaporization occurs only on the surface. • Boiling – when vaporization occurs below the surface. • The boiling point of a substance depends on the pressure of the air above it. a. In Denver, water boils at 95 degrees Celsius (203 degrees F)
B. Condensation – phase change when a gas becomes a liquid. 1. Occurs on a solid structure (glass, leaf, dust particle) 2. In clouds, tiny droplets of water form and stay afloat until they get heavy enough to fall.
III. Changes Between Solid and Gas • Sublimation – Change in phase from a solid straight to a gas. 1. Dry ice (frozen CO2)
FYI (you do not need to write this down) The reverse of sublimation is “deposition”