1. Chapter 7 Lesson 3 – “Physical Changes”
VOCABULARY
Physical change
Melting point
Boiling point
Sublimation
Condensation
Freezing
Deposition

2. What is a “physical change”?
WHEN MATTER CHANGES IN:
Size
Shape
Form
State of matter
AND…when the matter’s “identity stays the same.” (This means that the matter’s molecules DO NOT CHANGE.)

3. EXAMPLES OF PHYSICAL CHANGES: For each indicate if it is a change in size, shape or state of matter. Some might have more than one.
1. folding clothes
2. splitting firewood
3. melting a candle
4. freezing water
5. pouring juice from a bottle into a glass
6. cutting an apple

4. Answers: Shape Size AND shape Shape AND state of matter
THE MOLECULES IN ALL OF THESE DID NOT CHANGE

5. What causes a change in the state of matter?
A change in state of matter occurs when the movement of the particles changes.
WHAT CAUSES THE MOVEMENT OF THESE PARTICLES TO CHANGE?
Thermal energy must be added or removed

6. Adding Thermal Energy to a Solid
Particles in matter move faster
Temperature increases
Particles move so fast, they overcome forces that hold them close together
Solid reaches melting point and matter gradually becomes a liquid

7. What happens if thermal energy continues to be added?
See Fig. 11, page 250
What is being measured in this graph?
What is on x-axis?
What is on y-axis?
QUESTIONS:
What is happening to temperature in the first segment of the graph, as thermal energy is added?
What happens to temperature as thermal energy continues to be added while the matter is melting?

8. QUESTIONS (cont.):
3. What is happening to temperature in the third segment of the graph, as thermal energy is added to the liquid matter?
4. What happens to temperature as thermal energy continues to be added while the matter is boiling?
5. What is happening to temperature in the last segment of the graph, as thermal energy is added to the gas?

9. Adding Thermal Energy to a Liquid
Particles in matter move faster
Temperature increases
Particles move so fast, they overcome forces that hold them close together
Liquid reaches boiling point and matter gradually becomes a gas

10. Summarize:
When thermal energy is added to a solid, what happens to temperature?
Temperature rises until it reaches melting point.
When thermal energy is added to matter AS IT IS CHANGING STATE, what happens to temperature?
Temperature does NOT change because all of the energy being added is being used by particles to break free of their structure

11. More Summary
When thermal energy is added to a liquid, what happens to temperature?
Temperature rises until it reaches boiling point.

12. What is “sublimation?”
When a solid changes directly to a gas without first becoming a liquid.
EXAMPLE: solid iodine becomes a gas
Dry ice is another example. Solid CO2 becomes a gas.

13. Assignment: Due Tomorrow (Tues.)
Complete worksheet page 55 for tomorrow. You may leave #6 blank until after tomorrow’s class discussion.
LOOKING AHEAD:
Tuesday, 11/29 – Lesson 3 vocabulary quiz
Friday, 12/2 – Lesson 3 content quiz