1. Unit 2 Notes: Kinetic Molecular Theory

2. (1) The Kinetic Molecular Theory
Particles are in constant, random motion, resulting from their collisions with each other and surfaces.
Increase Heat Energy of Particles:
Increase amount of collisions
Increase amount of motion + speed
Decrease Heat Energy of Particles:
Decrease amount of collisions
Decrease amount of motion + speed

3. (2) EXAMPLE #1:
We saw this happen with the food coloring and the beakers of water…
Cold Water: Hot Water:

4. (3) Phases of Matter Solid: Liquid:
Has a uniform and organized structure.
Maintains shape.
Particles barely move.
Liquid:
Does not have a uniform or organized structure.
Only maintains shape inside a container.
Particles are free to flow and move in random directions.
Gas:
No shape.
Particles are spread out and move in random directions.

5. (4) EXAMPLE #2:
Let’s draw pictures to compare Solids to Liquids to Gases:
Solid: Liquid: Gas:

6. (5) Changing Phases
In order for a substance to “change phase”, it must either LOSE or GAIN heat energy.
Solid  Liquid  Gas:
Particles must GAIN heat energy
Particles move more, spread out more, and break structure
Gas  Liquid  Solid:
Particles must LOSE heat energy
Particles slow down, get close together, and align to structure

7. (6) EXAMPLE #3:
Let’s think about what happens when ICE MELTS…

8. (7) EXAMPLE #4:
Let’s think about what happens when you boil water…

9. (8) Types of Phase Changes:
Melting = Changing from Solid to Liquid
Freezing = Changing from Liquid to Solid
Evaporation = Changing from Liquid to Gas
Condensation = Changing from Gas to Liquid

10. (9) EXAMPLE #5:
Let’s think about what happens when shower steam CONDENSES on the bathroom mirror…

11. (10) EXAMPLE #6:
Let’s think about what happens when you make ice cubes…