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 FoilTable 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 Nitrogen Helium Carbon Copper Aluminum

1. Elements (continued) Each type of element has its own properties Cl = ChlorineCu = CopperBr = 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 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 = H 2 O Carbon dioxide = CO 2 Glucose = C 6 H 12 O 6

2. Compounds (continued) When ratios change, a different compound results – CO = carbon monoxide – CO 2 = carbon dioxide

2. Compounds (continued) Compounds have different properties than the individual elements that make them up + = Element Compound Silver (Ag) Chlorine (Cl) Silver Chloride (AgCl) Shiny, gray metalYellow/green gasSolid 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 Questions 1.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: H 2 O 2 and H 2 O. Do these formulas represent the same compound? Explain. 4. How does a heterogeneous mixture differ from a homogenous mixture? 5.Why is it correct to say that saltwater is a mixture? 6.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?