1. Warm-Up Please sit down quickly and quietly.
Please copy down the schedule in your Raven Book.
Next, answer this Warm-Up Question on your yellow sheet:
Explain what you think is a physical property. Name five physical properties of your desk.

2. Physical vs. Chemical Changes

3. Goal: How do you tell the difference between chemical and physical changes?

4. Physical Change* A change in any object’s physical properties
any change in an object’s:
- mass - color
- weight - shape
- volume - hardness
- density - texture

5. Physical Changes*
Changes in Density, Mass or Volume D = M/V

6. Physical Changes*
Creating mixtures that can be separated out - mixtures can be reversed.

7. Physical Changes*
Changes in Phase of Matter

8. Example of a Physical Change:
A Melting Icicle

9. physical properties = characteristics of a substance that can be observed without changing the identity of the substance.
ex.) wood is still wood whether it is shaped into a baseball bat or used to build the walls of your house – or if it’s still in the shape of a tree!
ex.) water is still water whether it is in the form of ice, liquid water, or water vapor. It’s still H2O!

10. Review: Other Physical Properties*
Color
Size
Shape
Texture
Magnetism

11. Chemical Changes*
Chemical Changes occur when atoms react with other atoms to form chemical bonds.
When atoms are bonded together they make a molecule.

12. Chemical Changes*
When a chemical reaction happens the new molecules are a new substance or compound.
A + B  AB

13. Chemical Change
> changes that substances undergo when they turn into other substances
> Also called a “Chemical Reaction”
ex.) as coal burns, O2 (in the air) combines chemically with C (the substance that makes up most of the coal) and forms a completely new substance = CO2
- C and O2 have changed chemically! They
no longer exist in their original forms!
- Written out: C + O2 = CO2

14. Evidence of Chemical Changes, Reactions or Bonding
Energy being taken in or given off (heat, coolness, light)

15. Evidence of Chemical Changes, Reactions or Bonding
Gas or Bubbles

16. Evidence of Chemical Changes, Reactions or Bonding
Color or Texture Change

17. Evidence of Chemical Changes, Reactions or Bonding
Color and Texture Change that is not easily reversed

18. Evidence of Chemical Changes, Reactions or Bonding
Forming of a Precipitate (adding to solutions and a solid is formed)

19. How to decide type of change
Ask yourself: Can I easily turn substance back to the way it was?
If yes: physical change
If no: chemical change
Was the change awesome to watch?
If yes: Probably chemical change
If no: Probably physical change
Did the name of the new substance change?
If yes: Probably chemical
If no: Probably physical

20. Examples of Chemical Change*
The rusting of iron
The baking of bread
Burning of a match
Fireworks

21. Example of a Chemical Change: The Electrolysis of Water (H2O)
The Chemical Identity of Water ( H2O ) is changed into the elements Hydrogen ( H2 ) and Oxygen ( O2 )

22. Homework: Complete in notebook
Physical or chemical change with explanation
Sugar water
Frying an egg
Whipping egg whites
Melting of dry ice
Burning gasoline
Boiling water
Breaking glass
Souring milk
Sun tanning
Boiling coffee

23. Copy the chart below for the lab tomorrow  (you need 10 rows)
Station
Substances combined
Observations
Physical or Chemical Change 1 2 3 4 5 6 7 8 9 10

24. Station # 1
Step 1 – measure 1 gram of baking soda and put it into the 100 ml beaker
Step 2 – measure 1 mL of vinegar
Step 3 – pour the 1 mL of vinegar into beaker with baking soda
Step 4 – observe what happens and record observations and inference about whether you think it is a physical or chemical change
Step 5 – clean up & rinse out the beaker and graduated cylinder in the sink

25. Station # 2
Step 1 – take a sheet of paper and drop it on to the ground – how many seconds does it take to hit the ground?
Step 2 – now crumple up the paper into a ball.
Step 3 – drop the paper ball from the same height you dropped the flat paper – how many seconds does it take for the crumpled ball to hit the ground?
Step 4 – observe what happens and record observations and inference about whether you think it is a physical or chemical change
Step 5 – clean up

26. Station # 3
Step 1 – take a tarnished penny and try to clean it with soap and water…does it work?
Step 2 – now try to clean it with a few drops of lemon juice…does it work?
Step 3 – rinse and dry the penny and try to clean it with water and salt…does it work?
Step 4 – now use a a few drops of lemon juice and a dash or two of salt to try to clean the penny
Step 5 – observe what happens and record observations and inference about whether you think it is a physical or chemical change
Step 6 – clean up, rinse and dry the penny and put the penny in the plastic container on the counter

27. Station # 4
Step 1 – take a the 100 mL beaker and fill it with water from the sink.
Step 2 – take one spoon full of table sugar and put it in the beaker with water.
Step 3 – stir the sugar in the solution until dissolved.
Step 4 – observe what happens and record observations and inference about whether you think it is a physical or chemical change
Step 5 – clean up & rinse out the beaker

28. Station # 5 Step 1 – put 50 ml of water into the beaker
Step 2 – drop 2 – 3 drops of food coloring into the water (one drop at a time) and watch
Step 3 –observe what happens and record observations and inference about whether you think it is a physical or chemical change
Step 4 – clean up & rinse out the beaker

29. Station # 6 Step 1 – measure out 10 mL of milk and pour into beaker
Step 2 – in a different graduated cylinder measure out 2 mL of vinegar and pour into the beaker with milk
Step 3 – stir the milk and vinegar together
Step 4 – observe what happens and record observations and inference about whether you think it is a physical or chemical change
Step 5 – clean up & rinse out the beaker and graduated cylinder in the sink