1. Phase Changes

2. Review: 4 Phases of Matter
Solid
Liquid
Gas
Plasma

3. What is a Phase Change? It is a change from one state of matter
(solid, liquid, gas) to another.
Phase changes are physical changes because:
- It only affects physical appearance,
not chemical make-up.
- Reversible

4. What happens during a phase change?
During a phase change, heat energy is either absorbed or released.

5. What is Exothermic change?
Heat energy is released as molecules slow down and move closer together.
Example: Gas to Liquid

6. What is Endothermic change?
Heat energy is absorbed as molecules speed up and expand.
Example: From solid to liquid

7. Types of Phase Changes

8. What is Melting? Phase change from a solid to a liquid
Molecules speed up, move farther apart, and absorb heat energy

9. What is Freezing? Phase Change from a liquid to a solid
Molecules slow down, move closer together and release heat energy.

10. Vaporization (Boiling)
Phase change from a liquid to gas. It occurs at the boiling point of matter.
Molecules speed up, move farther apart, and absorb heat energy.

11. What is Evaporation? Phase change from a liquid to a gas
Molecules speed up, move farther apart, and absorb heat energy.

12. What is Condensation? Phase change from a gas to a liquid.
Molecule slow down, move closer together and release heat energy.

13. Sublimation is? Phase change from a solid directly to a gas.
Liquid state doesn’t happen..!!!
Molecules speed up, move farther apart, and absorb heat energy.
Example:
As dry ice (frozen carbon dioxide gas)
gets warmer, it turns
into carbon dioxide gas

14. Deposition is? Phase change from a gas to a solid.
Again.. Liquid state doesn’t happen..!!!
Molecules slow down, move closer together and release heat energy.

15. Melting & Boiling Points
What is Melting Point:
The temperature at which a solid changes into a liquid.
What is Boiling Point:
The temperature at which a liquid changes into a gas.
What is a Freezing point?
Point at which liquid becomes solid.

16. Summary

17. Summary When Heat energy is released it is called? Exothermic change
Think of the prefix Exo as Exit

18. Summary When Heat energy is absorbed it is called? Endothermic change
The prefix endo means in

19. Graphing a Phase Change
Why is there no change in temperature
when changing solid to liquid and liquid to gas?
Because the heat energy is used get the molecules
to move faster and faster, until ice changes to liquid
and eventually liquid will change to gas

20. Graphing a Phase Change
Define melting point
* Melting Point happens when all the molecules
have so much energy that they now change
into the liquid state of matter

21. Graphing a Phase Change
What is the melting point and boiling point of water?
Pure Water melts
at 0 C or 32 F
Pure Water boils
at 100 C or 212 F
Graphing a Phase Change o o o o

22. Graphing a Phase Change
At what temperature does water freeze and become a solid?
Pure Water freezes at
0 C or 32 F o o

23. Directions
Take out your science notebook or your phone notes and write down the
following questions and answers

24. Assessment and Review…
1. Name six common phase changes.
Melting, freezing, vaporization, condensation, sublimation, and deposition.
2. What happens to the temperature of a substance during a phase change?
The temperature of a substance does not change during a phase change.
3. What is the difference between evaporation and boiling?
Evaporation takes place at the surface of a liquid and occurs at temperatures below the boiling point. Boiling point of pure water is 100 degrees Celcius

25. 4. How does the energy of a system change during a phase change?
Energy is either released or absorbed during a phase change.
5. What happens to the arrangement of water molecules as water melts and freezes?
The arrangement of molecules becomes less orderly as water melts and more orderly as water freezes.

26. 6. What is the difference between Endothermic and Exothermic change?
During endothermic change energy is absorbed
from the surroundings, such as hot stove
During exothermic change energy is released
into the surroundings
7. What are the freezing and boiling points of pure water
Freezing point is 0 degree Celcius and 32 degrees
Fahrenheit
Boiling point is 100 degrees Celsius and 212 degrees Fahrenheit

27. Homework tonight…… Complete: “Molecules on the move worksheet”
Write the correct Phase of matter and also include whether it was an Exothermic or Endothermic change
HW is due tomorrow..!! Oh yes..!