1. Physical & Chemical Changes
Changes in the properties of matter can be physical or chemical

2. Concept of Change Change: the act of altering a substance
Changes can be physical or chemical
When considering what TYPE of change has occurred…ask yourself:
“Did the identity of the substance change?

3. Physical Change
Physical change: a change that occurs that does not change the identity of the substance
Melting ice
Freezing Kool-aid
Tearing paper
Boiling water

4. A chemical change is called a chemical reaction
Chemical Changes
Chemical change: a change that occurs causing the identity of the substance to change
Burning paper
Digesting food
A chemical change is called a chemical reaction

5. Indicators of a chemical change:
Chemical Changes
Indicators of a chemical change:
Evolution of light
Evolution of heat
Evolution of a gas
Color change
Formation of a precipitate

6. Color Change Substance often change color during a chemical reaction.
Example: when gray iron rusts, the product that forms is brown.

7. Formation of a Precipitate
Precipitate: A solid product formed when chemicals in two liquids react.
Example: Seashells are formed when sea creatures release a liquid that reacts with seawater.

8. Formation of a Gas
Chemical reactions may produce a gas, like that often formed when antacid pills are mixed with excess stomach acid.

9. Temperature Change Most chemical reactions involve temperature change
Example: Concrete gets warmer as it hardens

10. Evolution of Light
Energy can be released in the form of light during a chemical reaction
Example—Glow Sticks

11. Is it Physical or Chemical?
Change
Physical
Chemical
Melting cheese
Burning wood
Milk souring
Wadding up paper
Bicycle rusting