States of matter and mixtures

• Solids

  • Tightly packed together in a regular arrangement
  • Vibrate in fixed positions
• Liquids


  • Close together but able to move past each other
  • Vibrate and move around each other
• Gases


  • Well separated with no regular arrangement
  • Vibrate and move freely at high speeds
• Particles in a solid

  Have the least amount of energy
• Particles in a gas

  Have the most energy
• Interconversion of state


  When matter changes from one state to another due to changes in temperature or pressure
• Melting

  Solid → liquid
• Freezing

  Liquid → solid
• Evaporation

  Liquid → gas
• Condensation


  Gas → liquid
• Solids


  Strong forces of attraction between particles which keeps them in their fixed positions
• Liquids

  Weaker attractive forces than in solids
• Gases

  Weakest intermolecular forces so particles are in random movement
• Physical change

  Involves changes in the forces between particles. The particles themselves remain the same and the chemical properties remain the same.
• Chemical change


  Affects the chemical properties of the substance
• Physical changes are relatively easy to reverse
• Sublimation


  When a solid changes straight into a gas
• Melting of a solid

  1. Particles absorb thermal energy which is converted into kinetic energy

  2. Particles in the solid vibrate more

  3. Solid expands until the structure breaks, and becomes a liquid
• Evaporation of a liquid

  1. Particles in a liquid expand

  2. Some particles on the surface gain sufficient energy to overcome the intermolecular forces and evaporate

  3. At the boiling point, all of the liquid particles gain enough energy to evaporate
• Substance A melts at -183oC and boils at -50oC. At -90oC, A is in the liquid state
• Mixture

  • Contains 2 or more elements or compounds that are not chemically combined together
  • The chemical properties of each substance in the mixture are unchanged
• Pure substance

  A single element or compound, not mixed with any other substance
• Melting point

  Pure substances have a sharp exact melting point

  Mixtures melt over a range of temperatures since they consist of several elements / compounds
• Simple distillation


  Used to separate a solvent from a solution. Useful for producing water from salt solution.
• Separating ethanol from water

  1. Distillation apparatus set up

  2. Mixture boiled

  3. Ethanol evaporates first

  4. Ethanol vapour cools in the condenser, condensing back to a liquid before being collected
• Fractional distillation


  Used to separate all the elements/compounds in a mixture. These chemicals must have different boiling points to be separated.
• Difference between fractional and simple distillation

  Simple distillation is used to separate a solvent from a solution.

  Fractional distillation is used to separate different liquids from a mixture of liquids, using their different boiling points.
• How fractional distillation works

  1. Oil is heated until it evaporates into the fractionating column

  2. Vapours rise up the fractionating column and condense at the different fractions, depending on the relative boiling point of each substance
• Filtration

  Used to separate an insoluble substance from a solution
• Separating an insoluble substance from a solution

  1. Place filter paper in a funnel

  2. Pour the solution containing an insoluble substance through the funnel into a conical flask

  3. The insoluble substance will collect on the filter paper and the solution will collect in the conical flask
• Crystallisation


  Used to separate a soluble solid from a solution if the solid decomposes when heated
• Separating a soluble solid from a solution if the solid decomposes when heated

  Use the process of crystallisation
• Separate an insoluble substance from a solution

  1. Place filter paper in a funnel

  2. Pour the solution containing an insoluble substance through the funnel into a conical flask

  3. The insoluble substance will collect on the filter paper and the solution will collect in the conical flask
• Crystallisation


  Process used to separate a soluble solid from a solution if the solid decomposes when heated
• Separate a soluble solid from a solution if the solid decomposes when heated

  1. Pour the solution into an evaporating dish and heat gently

  2. When the crystals start to form, remove the dish from the heat and leave to cool

  3. Once cold, filter the crystals out of the solution and leave them in a warm place to dry
• Chromatography


  Process used to identify soluble substances in a mixture
• Paper chromatography

  1. The mobile phase (solvent) moves through the stationary phase (paper) so anything dissolved in the mobile phase will move with up the paper

  2. Compounds interact differently with each phase so will move different distances through the stationary phase meaning they will be separated
• Chromatography

  Can show the composition of a mixture as different coloured substances will separate as they have different solubilities in the solvent and will travel at different rates
• Pencil should be used to draw the line along the bottom of the chromatography paper as it is insoluble in the solvent
• The water (solvent) in the beaker for paper chromatography should be no deeper than 1 cm deep to prevent washing away the substances placed on the line