1. Unit 3-2
Phase Changes

2. I. Phase Changes
A ____ase change is a ___ysical change that occurs when one phase (state) of matter changes into another.
Usually occurs when thermal (heat) energy is added or removed

3. c. Thermal energy is determined by how much the ______________ move.
i. In a _________the molecules move the ___________because they are closest together.
ii. In a _________ the molecules move the ___________ because they are furthest apart.
d. When we heat things up, molecules ______________which makes them _______________. This gives them more energy.
i. Example: heating up a solid makes the molecules go from close together to spread out (solid to a liquid).
-(Think of melting butter in the
microwave)

4. e. When we ______________heat (cool things down), the molecules move ____________which makes them move ______________. This gives them ______________________________.
i. Example- taking liquid water and freezing it. (liquid to a solid)

5. II. Heating Curve
To show phase changes, a ________________________is used.
A heating curve is a graph of ___________________________ against _________________.

7. F D E B C A Y TEMPERATURE (°C) Gas Liquid Solid X HEAT ENERGY
Interactive Heating Curve

8. 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

9. HEAT ENERGY
TEMPERATURE (°C) A B C D E F
What is happening during the steps where the temperature is constant (not changing)?
PHASE CHANGES!

10. III. Melting
This occurs when a ___________ changes to a _________________.
______________ in temperature (addition of heat energy) causes particles to move faster and farther apart so the molecules spread out.

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

12. IV. Freezing A _____________ changes to a _____________________.
Decrease in temperature (removal of heat energy) causes particles to move slower and closer together.

13. 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

14. V. Vaporization (Evaporation/Boiling)
A ______________ changes to a ____________________
__________________ in temperature (addition of heat energy) causes particles to move very fast and escape into the atmosphere.
There are 2 types-evaporation and boiling
i. Evaporation- only takes place on the surface of a liquid
-Example- puddle evaporating on a warm day
ii. Boiling- takes place on the surface and below the liquid.
-Example- boiling water

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

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

17. VI. Condensation A ____________ changes to a ______________________.
Decrease in temperature (removal of heat energy) causes particles to slow down to a point where they are in contact with one another.

18. 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

19. 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
Freezing B C

20. All together!

21. VII. Sublimation
________________changes DIRECTLY to a ________________ (with NO liquid phase in between)
Examples:
Dry Ice (frozen Carbon Dioxide)
Iodine

22. VIII. Deposition
______________changes DIRECTLY to a __________________ (with NO liquid phase in between)
Examples:
i. Snow-(air to ice)

23. VIII. Helpful Tip
Less dense to more dense = __________________ temperature
i. Gas to a solid
More dense to less dense = ________________ temperature
i. Solid to a gas

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

25. Deposition
Solid
Liquid
Gas
Sublimation

26. VIII. Important Temperatures
a. Melting Point – the temperature at which any more additional heat will cause a solid to melt.
Water (ice cube) 0° Celsius
Gold ° Celsius
Oxygen ° Celsius
Conversion from Celsius to Fahrenheit

27. b. ___________________– the temperature at which more heat removal will cause a liquid to change to a solid.
Water 0° Celsius
Gold ° Celsius

28. c. _________________– the temperature at which any additional heat will cause a liquid to change to a gas.
Water ° Celsius (212 F °)
Gold ° Celsius
Nitrogen ° Celsius
Oxygen °Celsius

29. 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

30. Some general thoughts….
As you move from ___________________, the heat energy increases over time.
Instead of raising the temperature, the heat energy is used to provide the molecules with more energy to move around.
As you move from ______________, the heat energy decreases (is lost to the environment, or atmosphere) over time.
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