1. Chemical and Physical Changes

2. Physical Change
Physical change: a change in some of the properties of a material but the composition of the material does not change
Reversible- a change that can be undone or reversed
Melting a substance
Irreversible- a change that is permanent or cannot be undone.
Cutting hair or cracking an egg

4. Learning Check: Which of the following is an example of a physical change?B. C. D.

5. Chemical Change
Chemical change: a change in which one or more substances change into a new substance, the composition changes
Chemical changes are also called chemical reactions

6. Signs of a chemical change
Precipitate (creation of solid)
Production of a gas
Change in color

7. Signs of a chemical change Cont.
Explosion or fire
Release of light or heat
Production of sounds

8. Learning Check: Which of the following is an example of a chemical change?
A. Chopping firewood
B. Opening a can of soda
C. Melting chocolate
D. Baking bread

9. Practice
Number your paper 1 – 10. Write chemical or physical for each and a description of the senario taking place.

10. 1. Is this a physical or chemical change?
dirt added to a puddle of water

11. 2. Is this a physical or chemical change?
making whip cream

12. 3. Is this a physical or chemical change?
baking soda fizzes with vinegar

13. 4. Is this a physical or chemical change?
sharpening a pencil

14. 5. Is this a physical or chemical change?
a stick broken into small pieces

15. 6. Is this a physical or chemical change?
sugar turns brown, then black with heat

16. 7. Is this a physical or chemical change?
using hot water to expand a metal cup

17. 8. Is this a physical or chemical change?
freezing water

18. 9. Is this a physical or chemical change?
cornstarch turns black with iodine

19. 10. Is this a physical or chemical change?
toasting a marshmallow