1. Phase Changes
“It’s just a phase”

2. States of Matter
Is defined as “a part of matter that has uniform properties through out the entire substance”
Solid, liquid and gas (and plasma)
Changes between states are called “phase changes”.
Caused by a change of heat or pressure. More often heat.
HEAT and TEMPERATURE are not the same thing.

3. HEAT and TEMPERATURE are not the same thing.
Measures the average kinetic energy of the particles in a substance.
Kinetic energy is directly related to the speed of the molecules.
The faster the particles/molecules are moving the higher the temperature.
Heat is a measure of energy (Joules).
For our class, higher temperature means more heat.

4. Solids Molecules are tightly packed together.
High potential energy – more bonds.
Molecules greatly affected by intermolecular forces.
Particles vibrate in place.
Very Dense.
Not easily compressed.

5. Liquids
Particles are not so tightly packed (liquids flow and can be poured).
Medium potential energy.
Particles are affected by intermolecular forces.
Surface Tension-ability of a liquid’s molecules to “stick” together.
Adhesion-stick to other compounds
Cohesion- stick to self

6. Gases Particles spread out as the container will allow.
High kinetic energy - particles are moving very quickly (1000 km/sec).
Little effect of intermolecular forces.
Low density, can be compressed, very fluid.

7. Comparison

8. Phase Changes When a substance changes state of matter.
Requires the input or the removal of energy (or change in pressure).
**During a phase change the temperature does not change, but the amount of energy does.
The energy goes toward breaking up weak intermolecular forces between the particles.
When two phases exist at the same time it is called equilibrium.

9. State Change Pyramid Gas Liquid Solid Condensation Sublimation
Absorbing
thermal energy
Releasing
thermal energy
Gas
Condensation
Sublimation
Vaporization
Melting
Freezing
Liquid
Solid

10. Changing States of Matter

11. Melting The change from a solid to a liquid.
The temperature at which a substance changes from a solid to a liquid is called the melting point.
Melting is when matter absorbs thermal energy.
Heat (energy) is added to matter the particles move faster till the bonds break.

12. Freezing The change from a liquid to a solid.
The temperature at which a substance changes from the liquid state to the solid state is called the freezing point.
Energy is released during freezing.
The attraction between the particles begins to pull the particles closer together and this is how the solid is formed.
After all of the liquid has become a solid, the temperature begins to decrease again.

13. Vaporization The change from a liquid to a gas.
The temperature of the substance does not change during vaporization.
The substance absorbs thermal energy.
Speeds up the particles throughout liquid to change to a gas.
2 types of Vaporization:
BOILING – matter changing from a liquid to a gas throughout the entire liquid.
EVAPORATION - matter changing from a liquid to gas on the surface of the liquid

14. Condensation The change from a gas to a liquid.
As a gas cools, its particles slow down.
When particles move slowly enough for their attractions to bring them together, droplets of liquid form.

15. Sublimation The change from a solid to a gas (skips liquid state).
The surface particles of the solid gain lots of energy quickly to become a gas.
Example – Dry Ice

16. Deposition
When a gas transforms into a solid without transitioning through a liquid state.
Energy is removed quickly, thereby changing from a gas to solid.
Example - Frost forming on windows.

17. Heating of Water – Phase Change

18. Cooling Curve Freezing Curve High Kinetic Energy Gas Condensation
Boiling
Liquid
Temp (C)
Freezing
Melting
Solid
Low Kinetic Energy
Time (min)

19. Heating Curve