Compounds, Molecules & Mixtures

• Molecule


  A group of two or more atoms that are held together by chemical bonds
• Molecules


  • Oxygen
  • Water
  • Nitrogen
  • Chlorine
  • Carbon dioxide
• Compound


  A substance that contains two or more different elements, with the atoms held together by chemical bonds
• Molecules


  Can be compounds if they contain two or more different elements
• Compounds


  • Water
  • Carbon dioxide
• Helium existing as a single atom would not count as a molecule</b>
• Compounds


  • The elements involved are always found in the same proportions
• Chemical formula


  Uses chemical symbols and numbers to represent the composition of a compound
• Chemical formulas


  • H2O
  • CO2
  • H2SO4
  • Ca(OH)2
• Some compounds can contain millions or billions of atoms
• Non-molecular compounds


  Compounds where the atoms are held together by ionic bonds, forming large structures rather than discrete molecules
• Mixture


  Two or more substances that are not chemically combined, just physically mixed together
• Mixtures can be separated using physical methods like filtration, crystallization or distillation