Chemical and Physical Changes

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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