CHEMISTRY P1

• Element


  All of the atoms are the same
• Elements


  • Magnesium
  • Sulfur
• Symbol


  Starts with a capital letter
• Compound


  Contains two or more different elements chemically combined in fixed proportions
• Compounds usually have totally different properties to the elements that they're made from
• Mixture


  Contains different elements or compounds, but they are not chemically combined
• Mixture


  • Magnesium atoms
  • Sulfur atoms
  • Magnesium sulfide
• Separation techniques for mixtures


  • Filtration
  • Distillation
  • Crystallization
  • Chromatography
• Molecule


  Any elements chemically combined, even if they are the same element
• Molecules

  • Methane
  • Water
  • Ammonia
  • Chlorine
  • Oxygen
• Molecules that are not compounds contain the same element chemically combined
• Chemical formula


  Tells us the elements in a molecule and the numbers of atoms of each element
• In a specific compound, the number of atoms of each element is fixed
• Interpreting a chemical formula

  1. Identify the elements

  2. Determine the number of atoms of each element
• Brackets in a chemical formula indicate that the numbers inside the brackets are multiplied by a number to the right of the brackets
• Physical separation techniques can only be used to separate mixtures, they cannot be used to separate the elements in a compound
• Chemical reactions such as reduction or electrolysis can be used to separate the elements in compounds
• Filtration


  Used to separate an insoluble solid from a liquid
• Insoluble


  The solid will not dissolve in the liquid
• Insoluble solid


  • Silver chloride
• Solvent


  • Water
• Filtration process


  1. Pour mixture into filter paper

  2. Liquid (filtrate) passes through

  3. Solid trapped in filter paper
• Crystallization


  Used to separate a soluble solid from a liquid
• Soluble solid


  • Sodium chloride
• Crystallization process


  1. Sodium chloride dissolves in water to form solution

  2. Water evaporates leaving behind solid sodium chloride crystals
• Heating can be used to speed up evaporation in crystallization, but care is needed as some chemicals may break down when heated
• Simple distillation


  1. Evaporate the liquid by heating

  2. Condense the vapor back to a liquid by cooling
• Simple distillation


  • Consists of two stages: evaporation and condensation
• Apparatus used for simple distillation

  • Flask containing solution
  • Continuous glass tube
  • Condenser with cold water circulation
  • Thermometer
• Steps in simple distillation

  1. Heat the solution to evaporate the liquid

  2. Vapor rises up the glass tube

  3. Vapor passes through the cold condenser and condenses back to a liquid

  4. Liquid collected in the beaker
• Simple distillation can be used to produce drinking water from sea water
• A great deal of energy is required for simple distillation, so it is generally not used to produce drinking water
• Other techniques are used instead of simple distillation to produce drinking water
• Fractional distillation


  A method used to separate a mixture of different liquids based on their different boiling points
• Fractional distillation


  • Requires a mixture of liquids with different boiling points
  • Uses a fractionating column containing glass beads to increase the separation of the liquids
• Fractional distillation process

  1. Heat the mixture

  2. Vapors with lower boiling point rise up the fractionating column first

  3. Vapors condense and drip back into the flask

  4. Repeated evaporation and condensation increases the concentration of the lower boiling point liquid

  5. Thermometer measures the temperature, which rises and then plateaus at the boiling point of the first liquid

  6. First fraction collected

  7. Temperature rises again, plateauing at the boiling point of the second liquid

  8. Second fraction collected
• If the two liquids have very similar boiling points, it is much harder to separate them and multiple rounds of fractional distillation may be required
• The equipment shown is not suitable for separating very large volumes of liquid, such as when refining crude oil
• Paper chromatography


  A separation technique used by scientists to separate substances in a mixture
• Paper chromatography is a physical process that does not involve chemical reactions and no new substances are made