1. Physical vs. Chemical Changes in Matter
How can we change the properties of a substance?

2. Physical Change Change in the physical properties of a substance
Examples
Crushing or breaking apart a substance
Change of state
Ice → water → water vapor
Dissolving a substance in a solvent
NO change in composition
Substance retains its original properties

3. Chemical Change
When 2 or more materials react and create new materials
Example – Baking
Mix together many ingredients
When you bake them, they form a completely new substance
New material has DIFFERENT PROPERTIES from those of the original substance(s)
Can not regenerate original materials

4. Evidence of chemical change
Complete change in color
Change in odor
Formation of a solid (precipitate)
Formation of a gas (bubbles)
Release or absorption of heat energy

5. Evidence of a chemical change
Example
Change in color
When bleach is added to the dye on a jacket a noticeable color change happens.
Change in odor
When a match is struck, the substances in the match react a give off a distinctive odor
Formation of a solid or gas
When vinegar is added to baking soda a carbon dioxide gas is formed.
Release or absorption of heat energy
When gas is burned heat is released.

6. Chemical or Physical Change?