1. Physical vs. Chemical Changes

3. Physical Change
A change that does not create a new substance
Most are easy to reverse

4. Examples bending (nail) crushing (can) cutting (paper)
dissolving (sugar)
freezing (ice)
melting (butter)
molding (clay)
pounding (metal)
mixing (kool-aid)
sanding (wood)

6. Chemical Changes
A change that creates new substances with different properties
Hard to reverse

7. Evidence of chemical changes
A new substance is formed
Change in odor (sour milk)
Change in color (jewelry, copper dome)
Production of heat (exothermic) (hand warmer)
Absorption of heat (endothermic) (cool pack)
Fizzing, foaming, bubbles (release of gas) (effervescent tablets)
Release of sound or light (fireworks)
Forms a precipitate (a solid from solutions)

8. Chemical Reaction
Sugar and Sulfuric Acid: Before and After!

10. Comparing Physical and Chemical Changes
Remember—Always ask yourself…did the composition (what makes up the material) change? If it did, a chemical reaction occurred. If it didn’t, a physical reaction occurred.

11. Let’s Practice—Decide whether each change is physical or chemical
Melting chocolate
Baking a cake
Burning a match
Adding kool-aid mix to water
Crushing a pill
Evaporating water
Digesting food
Making Jello
Burning gas in a car 

12. Using a cookie cutter to cut cookie dough
Baking cookies
The Statue of Liberty oxidizing
Molding play-dough
Leaves changing color in the fall
Metal rusting
Silver tarnishing
Turning water into ice
Cracking an egg
A battery working
Frying an egg

13. Cool Chemical Reactions
Gummy Bear Reaction
Halloween Clock Reaction
Sugar and Sulfuric Acid
6 Chemical Reactions that Changed the World PBS