Section 1: Describing Matter

What kinds of properties are used to describe matter?What are elements, and how do they relate to compounds?What are the properties of a mixture?

Compare the particles in each example:

• Aluminum Foil Table SaltWood

The most basic type of matter/can’t be broken down further

1. Elements• The building blocks of all matter in the

universe• Cannot be broken down into any other

substances

Elements

1. Elements (continued)• There are about 100 different types of

elements (listed in periodic table)Examples:• O = • N =• H =• C =• Cu =• Al =

Oxygen

NitrogenHeliumCarbonCopperAluminum

1. Elements (continued)

• Each type of element has its own properties

Cl = Chlorine Cu = Copper Br = Bromine

1. Elements (continued)

• Atoms = basic particles from which all elements are made

• Different atom = different element• Aluminum - Chlorine• Sodium - Oxygen

So, if there are only about 100 or so elements (building blocks) how come there are so many different examples

of matter (stuff)?

2. Compounds• When 2 or more elements combine

chemically (bonded together)

+ = Element Element Compound

Sodium Chlorine Sodium Chloride (salt)

2. Compounds (continued)• Atoms of the different elements are in a fixed

ratio

• Written as chemical formulas (letters and numbers)

Examples:• Water = H2O

• Carbon dioxide = CO2

• Glucose = C6H12O6

2. Compounds (continued)• When ratios change, a different compound

results

– CO = carbon monoxide

– CO2 = carbon dioxide

2. Compounds (continued)• Compounds have different properties than

the individual elements that make them up

+ =Element Element Compound

Silver (Ag) Chlorine (Cl) Silver Chloride (AgCl)

Shiny, gray metal Yellow/green gas Solid white crystals

Most of the stuff around us is NOT

or

but…Elements

Compounds

Mixtures

3. Mixtures

• Contain of 2 or more elements, compounds, or both in the same place

• The components are NOT combined chemically

3. Mixtures (continued)

• Easy to separate (magnets, filtering, evaporating)

• Example: saltwater (salt in water, but salt stays salt, water remains water)

3. Mixtures (continued)

• Each substance keeps its own properties (salt = white grains, water = clear liquid)

• Do not have to be in a fixed ratio (lots of salt or a little salt, its still saltwater)

3. Mixtures (continued)

• There are 2 Types of Mixtures:

1. Heterogeneous Mixtures- Different parts are visible- Examples: Salad

Soil Pencil

3. Mixtures (continued)

2. Homogeneous Mixtures- Evenly mixed, looks the same throughout- Examples: Saltwater

Air Brass

Practice Questions1. How are elements and compounds similar? How are they different?

1. Plants make a sugar compound with the formula C6H12O6. What elements make up this compound?

1. Look at the following chemical formulas: H2O2 and H2O. Do these formulas represent the same compound? Explain.

4. How does a heterogeneous mixture differ from a homogenous mixture?

1. Why is it correct to say that saltwater is a mixture?

2. Suppose you stir baking soda into water until the water looks clear throughout. How could you prove to someone that the clear material is a solution, not a compound?