Elements, Compounds and Mixtures

Diatomic Molecules - two atoms which bond together COVALENTLY
1. High melting point - means STRONG BONDS between particles
  1. Alloy - mixture of two or more elements at LEAST ONE OF WHICH IS A METAL
    1. HPLC - High Performance Liquid Chromatography
      1. Retention Time - the time each COMPONENT spends in the COLUMN
Elements
1. Only ONE type of atom
2. Cannot be simplified by chemical means
3. Two main kinds - metals and non-metals
4. Mixtures
  1. ORIGINAL properties of components REMAIN
  2. Have VARIABLE COMPOSITION
  3. Formation involves NO ENERGY CHANGE
  4. Compounds
    1. Two or more elements CHEMICALLY JOINED TOGETHER
    2. Made by CHEMICAL REACTIONS
    3. Have properties DIFFERENT FROM REACTANTS
Filtration - can be used to separate an INSOLUBLE LIQUID from a LIQUID
1. Recrystallisation/Evaporation - can be used to separate a SOLUTE from a SOLVENT
  1. Simple Distillation - used to separate a SOLVENT from the SUBSTANCES DISSOLVED IN IT
    1. Fractional Distillation - used to separate MISCIBLE LIQUIDS with DIFFERENT BOILING POINTS
      1. Separating Funnel - used to separate IMMISCIBLE LIQUIDS
        Chromatography - used to separate SOLUBLE SUBSTANCES which are VERY SIMILAR
Mass Spectrometers determine how heave the molecule is, and how it breaks up
Ability to identify a substance and ensure its purity is important -
1. to ensure purity of raw materials
  1. to check for adherence to claim on labels
    1. in drug design and manufacture
      1. to identify confiscated drugs and contraband
        to forensic scientists
Area under the peak in HPLC is proportional to the amount of the COMPONENT in the MIXTURE, and is used to monitor the concentration -
1. in drug testing in sport
  1. in environmental monitering
    1. in petrochemical industry
      1. in chemical, medical and biological research
Advantages of Instrumental Analysis -
1. Disadvantages of Instrumental Analysis -
  1. Instruments are extremely expensive
    1. Highly skilled chemists are required to use them
      1. Some compounds cannot be detected
2. Can use minute samples
  1. Fully automated
    1. Almost 100% accuracy

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