1. FOUNDATIONS OF CHEMISTRY
CHAPTER 7.3 pages
PHYSICAL CHANGES

2. Questions: How can a change in energy affect the state of matter?
What happens when something dissolves?
What is meant by conservation of mass?

3. Big Ideas Heating and Cooling
Adding or removing thermal energy can result in a change of state of matter. This change is state results from a change in the movement of particles that occurs as temperature rises or falls. Adding thermal energy causes particles to move faster. Removing thermal energy causes particles to slow down.

4. Big Ideas Dissolving Substances Conservation of Mass
When one substance dissolves in another, it creates a homogeneous mixture; this solution contains a solvent and one or more solutes. The particles of each solute completely dissolves and are evenly distributed throughout the solvent. The state of the solvent determines the state of the solution.
Particles of matter present before a physical change remain after the physical change. Water changing state from liquid to ice is an example. Another example is the formation of a mixture from two or more substances. In both examples, substances change but retain their masses.

5. Physical Change-
A change in size, shape, form, or state of matter in which the matter’s identity stays the same.

6. Change in Shape and Size
? How does a hamburger change in shape and size when you eat it?
? How does the shape of juice change when you pour it into a glass?
? How does a piece of wood change when you make a guitar?
Changes in shape and size are physical changes.
The identity of the matter does not change.

7. Changes in State of Matter
To change the state of matter, the movement of particles has to change.
To do this you have to either add thermal energy, or remove thermal energy.

8. Adding Thermal Energy
How do particles move when you add thermal energy?
When thermal energy is added to a solid, the particles in the solid move faster. This eventually overcomes the attractive forces holding the solid together and the solid reaches its melting point. Keep adding heat and the particles continue to move and the liquid reaches its boiling point.
they move faster

9. Some solids change directly to a gas without first becoming a liquid
Some solids change directly to a gas without first becoming a liquid. This process is called sublimation. An example is dry ice.

10. Removing Thermal Energy
How do particles more when you remove thermal energy?
When thermal energy is removed from a gas, such as water vapor, particle move slower and temperature decreases. Condensation occurs. Particles move slower and become attracted to each other. Keep removing energy and the temperature decreases more and the liquid turns to a solid.
they move slower

11. Key Concept patterns-
Freezing and Melting are reverse processes, and they occur at the same temperature.
The same is true of boiling and condensation.
Another change of state is deposition.
Deposition - the change from a gas directly to a solid. It is the opposite of sublimation.

12. Guess the state

13. Let’s learn a little about MATTER

14. Like many physical changes, dissolving is usually easy to reverse.
How would you get the salt out of salt water?

15. Law of Conservation of Mass

16. solution
solvent
solute
Answer: 30 g of solute dissolved

17. Explain why the graph has horizontal lines.
The horizontal lines indicate that the temperature of a substance does not change during a change of state.
DOK 2

18. End of Class or Homework
Complete the density column activity. *handout
You will not get to participate in the lab on Wednesday if this is incomplete.
Hint: underline the mass once and the volume twice
remember: liquid volume unit is mL
solid volume unit is cm3

19. answer to HW
1/23/2018