01- Experimental Chemistry

• Measurement of:

  • time: seconds (s)
  • temperature: Kelvin (K)
  • length: metre (m)
  • mass: kilogram (kg)
  • volume: cubic metre (m3)
• Measuring volume:

  • burette
  • pipette
  • volumetric flask
  • conical flask
  • measuring cylinder
  • beaker
• Pipette - used to transfer precise amounts of liquid from one container to another.
• Burette - used to measure small volumes accurately, usually less than 25 mL.
• Volumetric Flask - used to deliver exact volumes of liquids with high accuracy.
• collecting gases:

  • water displacement - insoluble to slightly soluble, density not impt
  • downward delivery - can be soluble or insoluble, denser than air
  • upward delivery - can be soluble or insoluble, less dense than air
• drying gases:

  • concentrated sulfuric acid, H2SO4 - not suitable for gases which react with sulfuric acid (e.g ammonia)
  • Quicklime (calcium oxide), CaO - must be freshly heated before use, cannot be used for gases which react with calcium oxide (e.g carbon dioxide)
  • Fused calcium chloride , CaCl2 - must be freshly heated before use, cannot be used for gases which react with calcium chloride (e.g ammonia)
• Separating Solid-Solid mixture

  • Magnetic attraction - separate magnetic solids from non-magnetic solids using a magnet
  • Sieving - separate solids with different particle sizes using a sieve
  • Suitable solvents - separate using suitable solvents in which only one of the solids is soluble in
  • Sublimation - separate a substance that changes from solid to gaseous state directly
• Separating Solid-Liquid mixtures

  • Filtration - separate insoluble solids from liquids
  • Evaporation to dryness - separate dissolved solid from its solvent by heating the mixture until all the solvent has vapourised
  • Crystallisation - obtaining a pure solid from its saturated solution
• Separating Liquid-Liquid mixtures

  • Separating funnel - separate immiscible liquids
• liquid-liquid mixtures

  miscible liquids - form uniform, homogeneous solutions when mixed

  immiscible liquids - form a heterogeneous mixture, can separate into layers known as phases if left undisturbed
• Pure substance: fixed boiling and melting point
• Separating Liquid-Liquid mixtures

  • Chromatography - separate a mixture of substances which have different solubilities in a given solvent
  • more soluble substances will move more rapidly towards the solvent front and the less soluble substances move at a slower rate, separating the mixture
  • Retention Factor: measure of substances solubility in a solvent, Rf, value=distance travelled by the substance/ distance travelled by the solvent (in decimals)
• Separating Solid-Liquid mixtures

  • Filtration - separate insoluble solids from liquids
  • liquid passing through the filter paper: filtrate
  • solid remaining on the filter paper: residue
• Separating Solid-Liquid mixtures

  • Simple distillation - separate a pure solvent(liquid) from a solution
  • liquid collected in the conical flask: distillate
  • boiling chips ensure smooth boiling
  • thermometer measures the temperature of vapour exiting the flask
• Separating Liquid-Liquid mixtures

  • Fractional Distillation - separate miscible liquids with different boiling points
  • The component with the lower boiling point will convert into water vapour more easily, therefore the component with teh lower boiling point will distill out first
• Types of mixture:

  • Solid-Solid
  • magnetic attraction
  • sieving
  • suitable solvents
  • sublimation
  • Solid-liquid
  • filtration
  • evaporation to dryness
  • crystallisation
  • simple distillation
  • Liquid-liquid
  • separating funnel
  • chromatography
  • fractional distillation