1. States of Matter 19-23 odd

2. Kinetic Molecular Theory  Explains how matter changes from Solid (s) → Liquid (l) → Gas (g)  There are spaces between particles of matter, and these particles are consistently moving.  All particles have energy. The amount of kinetic energy depends on whether it is a s,l,g.  Solids – least amount of kinetic energy  Gas- greatest amount of kinetic energy Remember kinetic = motion

3. Continued…  Temperature of a substance is a measure of the average kinetic energy. A drink at 25º C Majority of molecules at 25º C Some above and some below 25º C

4. Nature of Gases  Gas Pressure – result of collisions of many rapidly moving particles with walls of container (pascals, mmHg, atm)  Atmospheric Pressure- force of the weight from the air above.

5. Nature of Liquids  Key difference between gasses and liquids:  Gasses ≠ attractive forces (no defined volume)  Liquids = attractive forces (defined volume since atoms stay close together)

6. Vaporization/Evap/Boil  Vaporization of an element/compound is a phase transition from the liquid phase to gas phase.  Evaporation (below boiling)  Boiling (above boiling)

7. Evaporation  Evaporation is a phase transition from the liquid phase to gas phase that occurs at temperatures below the boiling temperature at a given pressure.  This process does not involve the addition of heat (kinetic energy)  Examples of evaporation:  Ice cubes in freezer, pool water, sweat

8. Evaporation continued…  When molecules collide they transfer energy to each other in varying degrees (based on how they collide).  Transfer of energy can be one sided  Molecules that receive enough energy can escape as vapor.  These molecules carry kinetic energy (heat) and therefore makes evaporation a cooling process (ex. Sweat)

10. Boiling (Vapor Pressure)  Boiling is a phase transition from the liquid phase to gas phase that occurs at or above the boiling temperature  Need to understand vapor pressure first:  Vapor Pressure: measure of the force exerted by a gas above a liquid

11. Boiling cont…  Boiling Point occurs when vapor pressure (pressure from escaping atoms) is equal to atmospheric pressure.  Standard boiling points of substances are expressed at 1 atm.  Ammonia -28.1ºF  Jet Fuel 350 ºF  Olive Oil 570 ºF

12. Changing Boiling Points You travel up a mountain to a higher elevation. It becomes harder to breathe because the amount of air molecules is less. You also notice your ears are popping due to the lower atmospheric pressure. You decide to make some hot chocolate. Will the cup of water boil at a higher or lower temperature here?

13. Lower! The water molecules have less atmospheric pressure that needs to be overcome by vapor pressure. Remember boiling when vapor pressure meets/exceeds atmospheric pressure. 32 F(Freeze) 212 F (Boil)

14. Nature of Solids  Fixed volume and shape  How do solids melt?  When heat is applied, particles vibrate rapidly due to the increase in kinetic energy.  Meting Point: point where solid changes to a liquid.  Note: the melting point and freezing point of a substance are equal.

15. Crystals  Solids form crystals  Crystals -particles arranged in an orderly repeating, 3D pattern.

16. Amorphous Solids  Not all solids form crystal structures  Amorphous solids lack ordered internal structure (rubber, plastic, asphalt, glass).

17. Allotropes  Two or more different molecular forms of the same element in the same physical state:  Carbon (diamond and graphite)