1. Physical and Chemical Changes
Unit II—Part 2

2. Concept of Change
Change: the act of altering a substance

3. Physical Change
Physical change: a change that occurs that does not change the identity of the substance
Melting ice (change in state or phase)
What do the particles look like when ice melts?
Freezing Kool-aid
Tearing paper
Boiling water (same as melting ice)

4. Chemical Changes
Chemical change: a change that occurs causing the identity of the substance to change
Burning
Digesting food
Reacting with other substances
(give an example per reviewer)
A chemical change is called a chemical reaction

5. Chemical Changes Cont’d
How do you know a chemical change has taken place?
Indicators of a chemical change:
Evolution of light
Evolution of heat
Evolution of a gas
Color change
Formation of a precipitate - creation of a solid

6. Is it Physical or Chemical?
Change
Physical
Chemical
Melting cheese
Burning wood
Milk souring
(Do all students relate to this?)
Wadding up paper
Bicycle rusting