Purity + Separating Mixtures

• all acids are mixtures
• in order for something to be an acid what does it have to do

  it needs to be dissolve in water
• what does aqueous (aq) mean

  that the substance dissolves in water
• describe the steps to separate a mixture of salt, sand and water

  1 use a filter and filter paper to filter the sand out of the mixture and leave the salty water residue in a test tube

  2 set up a Bunsen burner ; place it under a tripod with a mesh mat net and evaporation basin on top

  3 evaporate the residue on a roaring flame
• how does paper chromatography work

  1 draw a pencil line with dots of ink placed on it, on the chromatography and then roll up the top of the paper over a tooth pick and secure it with a paper clip

  2 place it in a beaker with water filled up to a pencil line
• by what physical property does distillation separate substances 


  based on their boiling point
• what state occurs during distillation

  evaporation and condensation
• why doesn't the gas escape in distillation

  the round bottom flask is sealed with a bun
• how is the gas returned to its liquid form in distillation

  it is condensed with the cool air in the water jacket
• What is chromatography used for

  to find the rf value of the ink in question
• what is an rf value

  the retention factor
• how to calculate the rf value

  the distance moved by the sample

  --------------------------------

  the distant moved by the solvent
• what is a solvent front


  the furthest point reached by the solvent
• what does a rf value of 0 mean

  it is insoluble
• what numbers does the rf value have to be between

  1-0
• what is the stationary phase in paper chromatography

  the chromatography paper
• what is the mobile phase in paper chromatography

  the solvent in the liquid state
• what type of graph is gas chromatography displayed in

  chromatograms
• what is purity


  the measure of how pure a substance
• what is a pure substance


  a substance consisting of one element or compound
• why are many useful materials mixtures 


  as they have been deliberately chosen to produce the desired properties
• how can a melting point be used to distinguish between pure or impure


  the melting point of a pure substance is a single temperature whereas the melting point of an impure substance can be over a range of temperature
• what is a solute 


  the substance that dissolves
• what is a solvent 


  the substance the solute dissolves in
• explain how filtration works 


  • separates an insoluble substance in the solid state from substances in the liquid state
  • works as filter paper has microscopic holes which the liquid molecules will be able to pass through but not the larger grains (solid substance)
  • the filter paper will collect the residue (solid substance) and the liquid will pass through as the filtrate
• explain how crystallisation works 


  • if you heat a solution, the solvent evaporates leaving the solute behind
  • it must be heated slowly otherwise you will end up with a powder
• explain how simple distillation works 


  • separates the solvent from the solution
  • it relies on the solvent having a lower boiling point than the solute so, when the solution is heated the solvent escapes the solution in the gas state
  • it is then cooled and condensed into a liquid state by a condenser
• explain how fractional distillation works 


  • separates 2 or more substances from a mixture in the liquid state
  • relying on each substance having a different boiling point, so when the mixture is heated both liquids rise however the one with the lower boiling point will evaporate quicker and not condense as much in the fractional column
  • then the substance with the lower boiling point will condense in the condenser
  • this process may be needed to be carried out multiple times to ensure pure substances are present
• Label this filtration experiment 


  A = funnel

  B = filter paper

  C = residue

  D = conical flask

  E = filtrate

  
• label this crystallisation experiment

  A = Bunsen burner

  B = boiling water

  C = evaporation basin

  D = solution

  
• label this simple distillation experiment

  A = solution

  B = vapour

  C = thermometer

  D = condenser

  E = cooling water out

  F = cooling water in

  G = test tube

  H = pure substance

  
• Label this fractional distillation experiment 


  A = solution

  B = fractionating column

  C = thermometer

  D = condenser

  E = cooling water out

  F = cooling water in

  G= pure solvent collecting beaker

  
• what is the only difference between paper chromatography and thin-layer chromatography 


  that the stationary phase is a thin layer of absorbent material coated over a plate
• how can chromatography be used to distinguish between pure and impure substances 


  after conducting paper or thin-layer chromatography, you can see if a substance is pure if it only creates one dot, whilst an impure substance will have two or more
• If your mixture contains: insoluble and soluble substances, what separation technique should you use


  filtration
• If your mixture contains: a solute dissolved in a solvent (solution), what separation technique should you use


  crystallisation for the solute

  simple distillation for the solvent
• If your mixture contains: two or more substances in the liquid state, what separation technique should you use


  fractional distillation
• If your mixture contains: coloured soluble substances, what separation technique should you use


  paper or thin-layer chromatography