Section 2.3 Classifying Matter Objectives/Goals: 1. To learn to distinguish between mixtures and pure substances 2. To learn methods of separation

A. Mixtures & Pure Substances Mixtures: something that has variable composition Ex: wood, soda, coffee, water, air Air: Neon, Helium, Nitrogen, Oxygen, Water vapor, Argon, Carbon dioxide

Alloys: mixtures of metals

Compound vs. Mixture A compound contains only particles of identical atomic composition; always has same composition. ex: Water (H2O) A mixture is a collection of compounds and/or elements that are present in various amounts. Has VARIABLE composition (depends what its made out of and how much)

Pure Substances- Always has same composition. (Either a pure element or a compound) Mixtures 2 or more pure substances Air Oxygen Nitrogen Water Argon Carbon Dioxide

Homogeneous & Heterogeneous Mixtures Homogeneous mixture: A mixture that is the same throughout (salt water, air, Kool-Aid) Solution: A homogeneous mixture Heterogeneous Mixture: A mixture containing regions with differing properties (oil & water, sand & water, chilli) *NOT UNIFORM THROUGHOUT

Mixtures & Pure Substances Pure Substance, homogeneous mixture, or heterogeneous mixture????? a. Gasoline b. A stream with rocks on the bottom c. Air d. Copper metal e. Maple syrup f. Oil and vinegar salad dressing g. Salt

B. Separation of Mixtures Distillation: A separation process that depends on the different boiling points of the substances Precipitate forms No chemical change occurs!

Filtration: Separation of a solid from a liquid by using filter paper Liquid passes through the filter paper, but the solid stays behind Physical change