1. Chemistry is the study of…
matter and its changes.
matter
anything that has mass and takes up space
Not matter?

2. Classifying matter All matter is either: a pure substance or a mixture
Mixtures may be separated by physical means.
ex) A salt water mixture may be separated by boiling away the water. (Taking advantage of the the much lower boiling point of water, compared to salt)
Pure substances may only be separated by chemical reactions.
ex) Separating hydrogen from oxygen in H2O requires a chemical reaction. The chemical bonds must be broken.

3. These are called “extensive” properties.
Pure substances have constant, “intrinsic” properties, which may be used to identify them.
Intrinsic = internal and constant.
Ex) melting point of gold = 1064 oC
density of gold = 19.6 g/cm3
(These properties are considered intrinsic because they never change, as long as we are talking about pure gold.)
Examples of properties that are not intrinsic = mass of a sample, shape, volume (These may vary between two samples of pure gold)
These are called “extensive” properties.

4. 2 kinds of pure substances
Elements: Made up of only one type of atom.
carbon, hydrogen, aluminum, etc.
Compounds: Made up of 2 or more atoms, chemically bonded.
CO2, H2O, NaCl

5. 2 kinds of mixtures heterogeneous: Particles are not mixed well.
You can usually see the different particles without magnification.
homogeneous:
Particles are mixed very well.
Difficult to distinguish from a pure substance simply by looking at it.

6. Try to classify the following as either: element, compound, heterogenous mixture or homogeneous mixture
Iron?
Stainless steel?
Wood?
Soda?
(what about the plastic or glass container?)

7. answer the following in your notes:
Which two classifications were the most difficult to distinguish from each other?
If you could investigate further, what would you do to be more certain of your answers?
In your own words, explain why it might be important (in chemistry) to know how to classify a substance.