1. Phase Changes

2. Review: 3 Phases of Matter
Solid
Liquid
Gas
Review: 3 Phases of Matter

3. What is a Phase Change? 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
What is a Phase Change?

4. What happens during a phase change?
During a phase change, heat energy is either absorbed or released.
Heat energy is released as molecules slow down and move closer together.
Heat energy is absorbed as molecules speed up and expand.
What happens during a phase change?

5. Types of Phase Changes
Types of Phase Changes

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

7. Freezing Phase Change from a liquid to a solid
Molecule slow down, move closer together and release heat energy.
Freezing

8. 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.
Vaporization (Boiling)

9. Phase change from a liquid to a gas on the surface of a liquid (occurs at all temperatures).
Molecules speed up, move farther apart, and absorb heat energy.
Evaporation

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

11. Sublimation Phase change from a solid to a gas.
Molecules speed up, move farther apart, and absorb heat energy.
Sublimation

12. Deposition Phase change from a gas to a solid.
Molecules slow down, move closer together and release heat energy.
Deposition

13. Number One
No video two
Number Three
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14. Phases is the term scientist use to more properly define solid, liquids and gases. It means the same as the term “state”
Phase is defined as “a part of matter that has uniform properties through out the entire substance”
Phases

15. As scientists we can change phases
As scientists we can change phases. We can change a solid into a liquid and a liquid into a gas.
When two phases exist at the same time it is called equilibrium.
Equilibrium is a dynamic condition in which two opposing changes occur in equal rates in a closed system
Phases change

16. To have equilibrium we need to have both a temperature and pressure.
When we have both a measured temperature and pressure two or three states will exist at the same time.
Ice melting into water, water freezing into ice.
Equilibrium

17. Scientist have phase diagrams to show exactly the temperature and pressure must be achieved to have a solid, liquid, gas, two phases or all three phases
A phase diagram by definition is “a relationship between physical states that deals with temperature and pressure.”
Phase Diagrams

18. Graphing a Phase Change

20. Melting & Boiling Points
Melting Point: The temperature at which a solid changes into a liquid.
Boiling Point: The temperature at which a liquid changes into a gas.
What is a Freezing point? Compare the freezing and melting points of water.
Melting & Boiling Points

21. Summary

22. Graphing a Phase Change
Why is there no change in temperature during a phase change?
Define melting and boiling points.
What is the melting point and boiling point of water?
At what temperature does water freeze and become a solid?
Graphing a Phase Change