Chapter 2 - Experiment Technique & Method of Purification

• The purity of the product can be determined by comparing its melting point
• If the melting points are identical, it is likely that the compound has been isolated pure.
• Crystallization from solvents other than water may also result in crystals being formed.
• Precipitation reactions involve adding a precipitating agent to a solution containing a soluble ion or molecule.
• Crystallization from solvents other than water may also be used to isolate compounds.
• Element

  Substance that cannot be broken down into simpler substances by chemical means
• Compound

  Substance formed when two or more different elements are chemically combined in a fixed proportion
• Mixture

  Combination of two or more substances that are not chemically combined and can be separated by physical means
• Mixtures


  • Easily separated
  • No fixed ratio/amount
  • Properties remain unchanged
• Compound


  • Chemically mixed
  • Hard to separate
  • Fixed ratio/amount
  • Properties change
• Solution

  Homogeneous mixture of a solute dissolved in a solvent
• Solute

  Substance dissolved in a solvent
• Solvent

  Dissolving medium in a solution
• Heterogeneous Mixtures

  distinguishable
• Colloid


  Mixture with insoluble tiny particles spread evenly throughout a liquid
• Suspension

  Mixture with insoluble solid spread throughout a liquid but quickly settles to the bottom
• Example of Suspension

  • Solid + liquid
  • Insoluble liquid in liquid (e.g. oil in water)
• Filtration

  Separate insoluble solid from liquid
• Buchner funnel

  1. Flask connected to suction pump

  2. Faster
• Decanting

  Pour liquid away, sedimentation, slow and inefficient
• Sieving

  Smaller particles pass through pores
• Sublimation

  Solid to gas (e.g. sulfur, iodine), only for substances that can undergo sublimation
• Centrifugation

  Separation based on density using centrifugal forces
• Simple distillation


  Separate solvent from solution based on boiling point
• Fractional distillation

  Separate miscible liquids based on boiling point
• Crystallization

  Concentrate solution until saturated, then crystals form
• Separating funnel

  Separate immiscible liquids
• Magnetic separation

  Separate magnetic from non-magnetic substances
• Chromatography

  Separate substances based on solubility and capillary action
• Rf value

  Distance travelled by substance/distance travelled by solvent
• Homogeneous


  indistinguishable