1. 2.5 Physical and Chemical Changes

2. Chemical Change
A chemical change is any change where you change a substance chemically.
A new substance is created
Example: Lighting a match

3. Evidence of a Chemical Change
Chemical Changes occur when:
…there is a change in color
… there is a production of gas
… there is a formation of a precipitate

4. Physical Changes
Physical Change- a change that takes place that does NOT change the substance chemically. Examples: haircut, ice melting

5. Physical Changes States of Matter Solids:
Have a definite shape and a definite volume
Slow molecules, low energy
Liquids:
Definite volume but not a definite shape
Medium energy molecules
Gases:
No definite shape, no definite volume
Fast molecules, high energy

6. Phase Changes
A phase change is a reversible physical change that occurs when a substance changes from one state of matter to another.
Energy is either absorbed or released during a phase change.
Endothermic – energy is absorbed
Exothermic – energy is released

8. Physical Changes
Melting: Solid to liquid, endothermic

9. Physical Changes
Freezing: Liquid to solid, exothermic

10. Physical Changes
Evaporation: Liquid to gas, endothermic

11. Physical Changes
Condensation: Gas to liquid, exothermic

12. Physical Changes
Sublimation: Solid to gas, endothermic

13. Physical Changes
Deposition: Gas to solid, exothermic