1. Phase Changes of Matter
Notes

2. 4 Phases of matter exist solid, liquid, gas, plasma (we don’t study)
Heat energy causes the physical properties to change into each of these phases

3. Properties of Phases Solid: has a defined volume and shape
Molecules have energy to vibrate, but not freely
When heated they expand; cooled they compress

4. Properties of Phases Liquid: Defined volume, but not a defined shape
Molecules flow and move, but stay close together
Heated they evaporate; cooled they condense

5. Properties of Phases Gases: Undefined volume and undefined shape
Molecules have energy to move fast and freely; they move away from each other
Heated they expand, cooled they compress

6. Properties of Phases Plasma: Rare on Earth
Extremely high energy & dangerous
Ex: the sun, lightning, fire

7. Properties of Phases Exothermic Change:
heat energy is released into the surroundings
Ex: water freezing…the water is not absorbing the cold…it is losing its heat.

8. Heat Energy & Phase Changes
Endothermic Change:
absorbs heat energy from surroundings
Ex: Ice melting…ice is absorbing heat from air around it and rising above the freezing point.
As the ice absorbs heat, the molecules of water move faster and start to flow away from each other

10. E D 100 gas C liquid B A solid Heat (thermal energy) Temperature º C.
As water changes from solid to liquid to gas, what is happening to the energy of the molecules?
(increasing) (click)
What is happening to the temperature?
(increasing) A
solid
Heat (thermal energy)

12. 6 Phase Changes Melting: Solid Liquid Vaporization: Liquid Gas
Occurs at melting point
Vaporization: Liquid Gas
Occurs at boiling point
Sublimation: Solid Gas
Does NOT change to Liquid phase in between
Ex: dry ice

13. 6 Phase Changes Condensation: Gas Liquid Freezing: Liquid Solid
Occurs when cooling to below boiling point
Freezing: Liquid Solid
Occurs at freezing point
Deposition: Gas Solid
Does NOT change to a Liquid in between
Ex: frost on car

14. Thermal Expansion
Tendency to change shape, area and volume through transfer of heat
Simply put: matter expands or contracts in size based on heat energy levels

15. Thermal Expansion Add heat = matter expands
Remove heat = matter contracts
Unique Quality of Water:
Water expands when it freezes.

16. Why does water expand when frozen?
Have you ever noticed ice cubes get larger than the liquid water they started as?
If you put a bottle of water in the freezer, it will expand and possibly rupture.

17. Try this at home: Remove cap from a water bottle;
Stand the bottle in a larger plastic dish(to catch the overflow);
Carefully put in freezer overnight
The ice should expand out from the mouth of the bottle.
WHY???

18. Why water expands when frozen.
As it freezes, it forms crystals, creating more space between molecules.