Classification of Matter by Composition

Matter by Composition

• Matter can be classified by composition into two broad groups: Pure Substances and Mixtures.

Pure Substances

• Definition: made up of only one component.
• Subtypes:
  • Element: cannot be chemically broken down; all atoms are the same throughout; example helium.
  • Compound: can be broken down into two or more elements in fixed ratios; definite proportions; composed of different elements.

Elements

• Simplest form of matter; cannot be chemically broken down; atoms identical throughout.

Compounds

• Consist of two or more elements in fixed, definite proportions; atoms of different elements combine.

Mixtures

• Definition: two or more components (elements or compounds); composition can vary.
• Subtypes:
  • Homogeneous: uniform throughout; looks the same; example sugar in water.
  • Heterogeneous: non-uniform; regions visually distinguishable (e.g., salt and pepper).

Separation of Mixtures

• Mixtures can be separated by physical means.
• Examples:
  • Magnetic separation: iron filings can be pulled from sand with a magnet.
  • Distillation and other physical methods (read about separating mixtures on page 8 in your book).