How is Matter Classified???

1. How is Matter Classified??? Ch. 1 Section 3

2. Classifying Matter • All matter is composed of atoms…the biggest atoms require more than 3 million to be as big as a millimeter • Atoms can be physically mixed or chemically joined

3. Pure Substances • characteristic properties to can be used to identify each • Both physical and chemical • Two types • Elements • Compounds

4. Elements • Pure substances that contain only one kind of atom • Each is represented by a chemical symbol • Some exist as a single atom (monatomic) • Ex. Helium gas - He • Some exist as molecules – two or more atoms combined in a definite ratio • Ex. Oxygen gas – O2 (diatomic) • Some exist in more than one form (allotropes) • Ex. Oxygen gas – O2 & Ozone gas - O3

5. Compounds • Composed of more than one atom • Ex. Carbon Dioxide – CO2 • Can be broken down into their elements…although difficult • Represented by a chemical formula • Always made up of the same kinds of atoms arranged in the same way

6. Mixtures • Contains two or more pure substances • Ex. Air – made up of mostly nitrogen and oxygen • Unlike chemically bonded compounds, the proportions of ingredients in a mixture vary • Variations cause differences in composition and properties • Ex. The solid mixture of gold (alloy) • 18 karat vs. 14 karat gold; 18 karat has 18 grams of gold per 24 grams = 75% gold by mass

7. Homogeneous Vs. Heterogeneous • Homogeneous Mixtures – pure substances are uniformly distributed throughout the mixture • Ex. Sweet tea and 14 karat gold • Heterogeneous Mixtures – contains substances that are not evenly mixed; different regions have different properties • Ex. Water and sand, and chocolate chip ice cream