1. Elements, Compounds, and Mixtures

2. What is a Pure Substance?
A pure substance is composed of a single type of material  elements & compounds
Examples: water, diamond, gold, table salt, bronze
Pure substances cannot be separated by physical means (distillation, filtration, and chromatography)

3. What is an Element? We have already studied elements
An element is a pure substance containing only one kind of atom
As of now, 118 types of elements are listed and classified on the Periodic Table
Examples?

5. What is an Element? Elements are always homogenous –
the composition is identical wherever you sample it, uniform all the way through in composition and properties
An element cannot be separated into simpler materials

6. What is a Compound?
A compound is a pure substance that is created by 2 or more kinds of atoms
The atoms are chemically combined by reacting with one another, forming molecules
Examples: NaCl, H2O, CO2, NH3, NaHCO3, and C6H12O6
Compounds cannot be separated by physical means without a chemical reaction

8. Why Do Compounds Form?
Elements will form compounds to become more stable.
Na is flammable in water
Cl2 is a toxic gas
NaCl is a very stable compound that is neither flammable nor toxic
Properties of a compound are usually different than the properties of the elements it contains
Compounds that are unstable will break down to form more stable elements

9. Why Do Compounds Form?
Compounds form when valence electrons in the outermost shell of 2 or more elements interact
THE OCTET RULE: an element is most stable with 8 valence electrons
Elements will join chemically to get 8 valence electrons

10. Example: CO2 Oxygen (O) has 6 valence electrons Carbon (C) has 4 valence electrons If carbon shares 2 electrons with each oxygen, everyone will have 8 valence electrons!

11. *REMEMBER: solution = solute + solvent*
What is a Mixture?
A mixture is the physical combination of 2 or more elements or compounds – NOT chemically combined (no reaction between substances)
Mixtures can be evenly distributed or not:
uniform (homogeneous) = solutions
non-uniform (heterogeneous)
*REMEMBER: solution = solute + solvent*

13. What is a Mixture?
The properties of a mixture are similar to the properties of its components
Ex: Salt water
NaCl = salty
H2O = clear liquid
Salt water = clear, salty liquid!
Mixtures can be separated by physical means (filtration, distillation, and chromatography)

14. Homogeneous Mixtures: Heterogeneous Mixtures:
EXAMPLES!
Homogeneous Mixtures:
Heterogeneous Mixtures:
Rain
Steel
Air
Vinegar
Salt water
Whipped cream
Cereal
Ice in soda
Soil
Pizza
Box of toys
You

15. Classifying Matter… Matter Pure Substances Mixtures milk, tea Fe, O
Elements
Compounds
Homogeneous
Heterogeneous
Rocky Road ice cream, muddy water
milk, tea
Fe, O
H2O, CO2