2. Do you Remember the Clues for a chemical change?

3. 1. New Colour 2. Heat/Light 3. Precipitate Forms 4. Gases bubbles form 5. Difficult to reverse

4. Chemical reactions can be desirable (good) or undesirable (bad)

5. Desirable Reactions 1. Photosynthesis

6. 2. Cellular Respiration

7. 3. Fireworks

8. 4. Chlorine (in pool water keeps bacteria and algae populations under control),

9. 5. Toothpaste (sodium fluoride in toothpaste reacts in your mouth to rebuild enamel and control bacteria

10. 6. Soap and shampoo (has sodium or potassium which clean dirt and oils off your body

11. Undesirable Reactions 1. Food Spoilage

12. 2. Rusting

13. 3. Acid Rain