Chemistry 2.1

• Element


  A simple substance that cannot be broken down into smaller substances
• There are 92 elements
• Atom


  The smallest part of an element
• Molecule


  The smallest part of a compound
• Compound


  A pure substance containing atoms of different elements chemically joined
• Compounds


  • H2O (water)
  • Copper sulfide
• Atoms of copper and sulfur make up copper sulfide
• The periodic table shows elements
• Compounds


  • H2O = 2x Hydrogen 1x Oxygen
  • NaOH = 1x Sodium 1x Oxygen
  • C2H5OH = 6x Carbon 5x Hydrogen 1x Oxygen
• Ions


  Atoms or molecules with a net electric charge
• Ionic compounds


  • Magnesium oxide = Mg2+ O2-
  • Calcium chloride = Ca2+ 2Cl-
• Relative atomic mass


  The mass of an atom of an element compared to other elements
• Relative molecular mass (RMM)


  The mass of a molecule calculated by adding the atomic masses
• Calculating percentage composition


  Find the percentage of each element in a compound
• Balancing chemical equations involves adding coefficients to ensure the same number of atoms on each side
• Methods of separating mixtures

  • Filtration
  • Evaporation
  • Simple distillation
  • Chromatography
• Rf value


  Ratio of the height of the solute to the height of the solvent in chromatography
• Mole


  Unit used to measure the amount of a substance, equal to 6.02 x 10^23 particles
• 1 mole of an element has a mass equal to its relative atomic mass in grams
• Calculating moles


  Moles = Mass / Molecular mass
• Avogadro's number is 6.02 x 10^23
• Calculating moles in reactions


  • Example 1: Calculating the formula of aluminium fluoride
  • Example 2: Determining the ratio of elements in a compound