Classification of Matter

Two classifications of matter are a pure substance or a mixture defn. Mixture: A blend of two or more kinds of matter, each of which retains its own identity and properties. Most everyday items would be considered mixtures. Examples: air, sugar water, soup, and gasoline.

defn. Pure substance: Has a fixed composition and differs from a mixture in the following ways: 1. Every sample of a given pure substance has exactly the same characteristic properties. EXAMPLE: Every sample of pure water has the same boiling point. 2. Every sample of a given pure substance has exactly the same composition EXAMPLE: Pure water always has a 2 to 1 ration of hydrogen to oxygen. It also has 88.8% oxygen and 11.2% hydrogen by mass.

MIXTURES Mixtures can be placed into two categories, Homogeneous or Heterogeneous defn. Homogeneous: Mixture is uniform in composition, is also referred to as a Solution. Example: Sugar water, chlorine water. ** Homogeneous Mixtures can sometimes be confused with a Pure Substance. **

defn. Heterogeneous: A heterogeneous mixture is not uniform in composition. Example: Oil and Water, Soup, dirty water. Some mixtures can be separated by filtration or vaporization

PURE SUBSTANCES A pure substance will always be homogeneous and will either be a compound or an element. defn. Compound: A compound can be decomposed or broken down into two or more simpler compounds or elements by a chemical change. Example: Water….can be broken down into hydrogen and oxygen by electrolysis. defn. Element: A pure substance that cannot be decomposed or broken down by a chemical change. Example: Hydrogen, Oxygen, Carbon