2. Physical Change
Chemical Change
Changing the form of the substance. The substance is still the same thing, and it can easily be reversed.
Changing what the substance is, how the atoms are connected. Difficult to reverse.
Ex: melting, boiling, bending, dissolving.
Ex: burning, rusting, cooking, changing color, making a gas.

3. Properties
Characteristics that allow you to distinguish one kind of substance from another.
Physical Properties
Chemical Properties
Characteristics we can observe without altering the identity of the substance
Characteristics we can only observe by changing the substance into something else (by a chemical change)
Ex: Color, smell, taste, size, shape, density, solubility
Ex: Flammability, reactivity

4. Try it: Chemical or Physical Change?
Rubbing alcohol evaporates quickly from the skin.
Frying an egg.
Boiling Water.
Burning gasoline.
Breaking Glass.
Salt dissolving in water.
Copper reacts with Sulfur to form Copper Sulfide.
Kicking a dent in Mr. Yusten’s car door.
Watching Mr. Yusten’s car door rust.

5. Definitions Matter Anything that has mass and takes up space.
AKA stuff. NOT ENERGY!
How much “stuff” is there. (Not how much it weighs, but related)
Mass
Volume
The space something takes up.
Density
How much mass there is per volume.
AKA the amount of stuff in a given space.

6. Density
A physical property of a substance. It is always the same for the substance, no matter what form it is in…
We can use it to identify something!
Example: What is the density of a block of wood that has a mass of 72 grams and a volume of 134 mL? (remember sig figs!)

7. Measuring Volume
Solid: If it is uniform (has straight sides):
L x W x H
If it is not uniform:
Water Displacement in a graduated cylinder.
Liquid: graduated cylinder.
Gas: collect in a closed container.
Note: cm x cm x cm = cm3 = mL

8. Material
Density (g/ml or g/cm3)
Hydrogen
Air
Gasoline
0.70
Ice
0.92
Water
1.00
Milk
1.03
Aluminum
2.70
Iron
7.80
Lead
11.30
Mercury
13.60
Osmium
22.50

9. Percent Error
No measurement is perfect! Instrument accuracy, precision, even you!
Never blame “human error.” Always state exactly where you might have had an error!