1. Unit 3-2
Matter and
Phase Changes
Mr. Coffey

2. Remember matter?
Matter is defined as anything that has mass and takes up space (has volume!).
Matter is made up of molecules that can move
Molecules are groupings of atoms; the small pieces that make stuff up!
The molecules in EVERYTHING are moving – even if we can’t see or feel them moving!

3. Solids Solids have a definite volume and shape
That means that if left alone, their shape won’t change
Ex: the size & shape of a building doesn’t change
The molecules are packed closely together

4. Amorphous Solids
These are solids that DO NOT keep their definite shape.
Wax, Tar, & Glass

5. Liquids
Have a definite volume and fill a definite amount of space – but their shape will change based upon their container!
If you pour a liquid from one container to another it will change its shape but still be the same amount!

6. Gasses They have no definite shape or volume
They will completely fill whatever container they are in which causes volume to increase & decrease.
The molecules can spread out or be pushed together
Gas molecules are constantly hitting each other & colliding with the wall of their containers

7. Plasma
Matter existing at extremely high temperatures; it is very rare on earth
Found mainly in stars – very high energy sometimes causes chemical bonds to break.
Neon lights are plasma! Noble gases are excited by the electricity that passes through creating plasma
Plasma TVs are PLASMA!

8. YES YES NO YES NO NO Sum it up! State of Matter Definite VOLUME??
Definite SHAPE??
SOLID
LIQUID
GAS
YES
YES NO
YES NO NO

9. Arrangement of Particles

10. How do phases/states CHANGE?
Substances can change their state when thermal energy is added or subtracted.
Thermal Energy is how much energy something has because of how much it’s molecules move.
When we heat things up the molecules move faster!
Because the molecules move faster, they move apart!

11. Continued…. Note: heat will always move from WARM to COLD
When substances are heated, the attractive forces weaken…..so the molecules move AWAY from each other!

12. + or – Thermal Energy
If we add or subtract thermal energy, we can force a phase change to happen!
Cooling = taking away energy
Heating = adding energy
Temperature is the measure of the amount of heat in an object, remember there is no such thing as cold….only LESS HEAT
Temperature is the measure of how fast molecules move – average KINETIC ENERGY!

13. The Molecules
Molecules in a solid are packed close together, as they heat up they move apart

14. Phase Changes Phase changes are physical changes.
Changing states of matter:
SOLID LIQUID GAS

15. Y F D E
Gas
TEMPERATURE (°C) B C
Liquid
Solid A X
HEAT ENERGY

16. A B C D E F A B Yes D E No B C No E F Yes C D Yes
Is the temperature changing from:
HEAT ENERGY
TEMPERATURE (°C) A B C D E F
A B
Yes
D E No
B C No
E F
Yes
C D
Yes

17. What is happening during the steps where the temperature is constant (not changing)?
PHASE CHANGES!

18. From left to right (absorbing energy)
HEAT ENERGY
TEMPERATURE (°C)
Solid
Liquid
Gas A F
From left to right (absorbing energy) B C D E
MELTING B C

19. From left to right (absorbing energy)
HEAT ENERGY
TEMPERATURE (°C)
Solid
Liquid
Gas A F B C D E
VAPORIZATION D E

20. From right to left (losing energy)
HEAT ENERGY
TEMPERATURE (°C)
Solid
Liquid
Gas A F
From right to left (losing energy) B C D E
Freezing B C

21. From right to left (losing energy)
HEAT ENERGY
TEMPERATURE (°C)
Solid
Liquid
Gas A F
From right to left (losing energy) B C D E
Condensation D E

22. If this diagram is for water (H20)…Y
HEAT ENERGY
TEMPERATURE (°C)
Solid
Liquid
Gas A F B C D E
0°C
100°C

23. All together!

24. Let’s Review! Solid Liquid Gas Freezing Condensation Melting
Vaporization

25. Deposition
Solid
Liquid
Gas
Sublimation

26. Terms to know Phase Change Definition Thermal Energy Melting Add
Solid  Liquid
Add
Freezing
Liquid  Solid
Subtract
Vaporization
Liquid  Gas
Evaporation
Boiling
Condensation
Gas  Liquid
Sublimation
Solid  Gas

27. What we all want to know!
Question: For water, why does the temperature remain unchanged at 0°C when it is melting (solid to a liquid)?
Answer: In order to go from a solid to a liquid, the molecules use the HEAT ENERGY to change the arrangement of particles from:
The temperature does not increase because the heat is being used for this!

28. What we all want to know!
Question: For water, why does the temperature remain unchanged at 0°C when it is freezing (liquid to a solid)?
Answer: In order to go from a liquid to a solid, the molecules release the HEAT ENERGY as the arrangement becomes more rigid:
The temperature does not decrease because the heat is being released for this!

29. The same is true for vaporization and for condensation!

30. Some general thoughts….
As you move from left to right, the heat energy increases over time.
As you move from right to left, the heat energy decreases (is lost to the environment, or atmosphere) over time.
In general, the greater the heat energy, the greater the temperature, and the lesser the heat energy, the lesser the temperature.

31. Phase Changes
As you go from left to right, the heat energy increases. During phase changes (melting and vaporization), the heat energy is not used to raise the temperature.
Instead of raising the temperature, the heat energy is used to provide the molecules with more energy to move around.

32. Phase Changes Continued
As you move from right to left, the heat energy decreases. During phase changes (condensation and freezing), the loss of heat energy is not seen on a thermometer (no decrease in temperature).
Instead, the heat energy is lost because the molecules are becoming more rigid, and they do not need the extra energy for particles to move around.