Observing Physical & Chemical Changes pages 21-27 and 163-169

1. Observing Physical &Chemical Changespages 21-27 and 163-169

2. Physical Changes • A substance may LOOK different (different size, or shape) but NO new substance is formed • The composition is NOT changed! • ATOMS do NOT change the way they are linked up • Can (sometimes) be REVERSED

3. SIGNS to indicate a Physical Change • Changing STATE • DISSOLVING • Changing SIZE, SHAPE, FORM

4. Examples of Physical Changes(mark all that apply) • Drying wet clothes • Lighting a match from a matchbook • Cutting snowflakes out of paper • Melting butter for popcorn • Getting your hair colored at the salon • Dissolving sugar into iced tea

5. Examples of Physical Changes(mark all that apply) • Drying wet clothes • Lighting a match from a matchbook • Cutting snowflakes out of paper • Melting butter for popcorn • Getting your hair colored at the salon • Dissolving sugar into iced tea

6. Chemical Changes • A NEW substance is created with different properties because a chemical reaction took place • The composition of the substance changes! • ENERGY is always taken in or given off! • ATOMS change the way they link up • Are NOT easily REVERSED (would take another chemical change in some cases to do so)

7. SIGNS to indicate a Chemical Change • Burning • Bubbling/fizzing, which means presence of a GAS • Formation of a PRECIPITATE • An unusual/foul ODOR can occur when a chemical change takes place • ENERGY is gained/released • Total COLOR change may occur

8. Examples of Chemical Changes(mark all that apply) • Burning paper turns to ash • Water boiling on the stove • Curdled milk • Copper pennies turning green • Bread dough rising (gas formed as yeast reacts w/ sugar)

9. Examples of Chemical Changes(mark all that apply) • Burning paper turns to ash • Water boiling on the stove • Curdled milk • Copper pennies turning green • Bread dough rising (gas formed as yeast reacts w/ sugar)

10. Teacher Demo #1 Ice Ice Baby Is this a physical or chemical change? PHYSICAL Give evidence (signs) to support your answer. Melting is a change of state

11. Teacher Demo #2 I want to be rich Is this a physical or chemical change? CHEMICAL Give evidence (signs) to support your answer. Burning

12. Teacher Demo #3 Sugar Daddy Is this a physical or chemical change? PHYSICAL Give evidence (signs) to support your answer. Dissolving

13. Teacher Demo #4 Alka-seltzer Is this a physical or chemical change? CHEMICAL Give evidence (signs) to support your answer. Bubbling/fizzing, presence of a gas

14. Are the following changes Physical “P” or Chemical “C”? • _________- a pear turning brown • _________- cookie batter baking to a golden brown • _________- a frozen pond melting • _________- a marshmallow burning • _________- fireworks lighting up the sky • _________- cutting your hair • _________- eggs spoiling • _________- dissolving food coloring in water • _________- rusting of a metal bike • _________- wood burning in your fireplace • _________- frozen CO2 (dry ice) turning into a gas • _________- crushing a Coke can • _________- boiling a pot of water • _________- leaves changing color in the fall • _________- experiencing body odor (BO Charlie)

15. Are the following changes Physical “P” or Chemical “C”? • ____C_____- a pear turning brown • ____C____- cookie batter baking to a golden brown • ____P_____- a frozen pond melting • ____C_____- a marshmallow burning • ____C_____- fireworks lighting up the sky • ____P_____- cutting your hair • ____C_____- eggs spoiling • ____P_____- dissolving food coloring in water • ____C_____- rusting of a metal bike • ____C_____- wood burning in your fireplace • ____P_____- frozen CO2 (dry ice) turning into a gas • ____P_____- crushing a Coke can • ____P_____- boiling a pot of water • ____C_____- leaves changing color in the fall • ____C_____- experiencing body odor (BO Charlie)

16. The Law of Conservation of Mass During a chemical or physical change, matter is not created or destroyed. In 1774, this principle was 1st demonstrated byAntoine Lavoisier

17. We Love Chemistry!