Mixtures

• If you put two or more different substances together and they haven’t reacted, they have likely to have formed a mixture.
• Because mixtures are not chemically bonded they can be easily separated using physical methods like filtration, crystallisation or distillation
• • A mixture is a combination of two or more substances that are not chemically joined together
  • These substances can be elements and / or compounds

  Examples of mixtures

  
• Mixtures can be just elements, just compounds or elements and compounds, but the substances must not be chemically joined together
• A physical method of separation does not produce a new substance as there is no chemical reaction taking place since no chemical bonds are being broken or formed.
• Because in mixtures substances are not chemically bonded together This means that mixtures can be easily separated by physical processes such as:

  • Filtration
  • Evaporation
  • Distillation
  • Chromatography
  • The physical process that is used for separation depends on the substances being separated
• • Filtration is used to separate an insoluble solid(can’t dissolve) from a mixture of the solid and a liquid
  • For example, sand from a mixture of sand and water
• Filtration method

  • A filter paper is placed in a filter funnel above a beaker
  • The mixture of insoluble solid and liquid is poured into the filter funnel
  • The filter paper will only allow liquid particles and soluble solids to pass
  • The liquid that passes through into the beaker is called the filtrate
  • Insoluble solids (sand) do not pass through the filter paper and are left behind as a residue
• 1. Crystallisation method The solution is heated in an evaporating basin placed on top of a tripod which is on top if a Bunsen burner ,allowing the solvent to evaporate and leaving a saturated solution behind You can test if the solution is saturated by dipping a clean, dry, cold glass rod into the solution

  • If the solution is saturated, crystals will form on the glass rod when it is removed and allowed to cool
• Crystallisation method 


  2.

  • The saturated solution is allowed to cool slowly
  • Solids will come out of the solution as the solubility decreases
  • This will be seen as crystals growing
• Crystallisation method 


  3.

  • The crystals are collected by filtration
• Crystallisation method 


  4. They are then washed with distilled water to remove any impurities
• Crystallisation method 


  5.

  • Finally, they are allowed to dry
  • Common places to dry crystals are between sheets of filter paper or in a drying oven
• Crystallisation is used to separate a dissolved solid from a solution
• • Distillation is used to separate a liquid and soluble solid from a solution (e.g. water from a solution of saltwater) or a pure liquid from a mixture of liquids
• Simple distillation method

  1. The solution is heated with a Bunsen burner in a round bottom flask and pure water evaporates (once the water reaches its boiling point, 100 degrees- measured by thermometer) producing a vapour which rises through the neck of the round-bottomed flask
• Simple distillation method 


  2.

  • The vapour passes through the condenser, where it cools and condenses, turning into pure water which is collected in a beaker
• Simple distillation method 


  3.

  • After all the water is evaporated from the solution, only the solid solute will be left behind
• • Simple distillation can be used to separate the products of fermentation, such as alcohol and water
• • Simple distillation can be used to separate the products of fermentation, such as alcohol and water
• • fractional distillation is a more effective separation technique, commonly used when the boiling points of the liquids are close and/or a higher degree of purity is required, such as crude oil
• Simple distillation apparatus

  
• Crystallisation apparatus

  
• Filtration apparatus

  
• Fractional distillation is used to separate two or more liquids that are mixed with one another 
• Fractional distillation ethanol and water

  1. The solution is heated ( with an electric heater instead of a Bunsen burner. This is because ethanol is flammable). The solution is heated to the temperature of the substance with the lowest boiling point (ethanol 78 degrees). To check this a thermometer is used
• Fractional distillation ethanol and water

  2.

  • This substance (ethanol)will rise and evaporate first, and vapours will pass through a condenser, where they cool and condense, turning into a liquid that will be collected in a beaker
• Fractional distillation ethanol and water 


  3.

  • All of the substance (ethanol) is evaporated and collected, leaving behind the other components(s) of the mixture
• Fractional distillation ethanol and water 


  4. Pure water is now left behind in the round- bottom flask
• Fractional distillation apparatus

  
• The chemical properties of each substance in the mixture is unchanged