1. States of Matter

• solids:

  arrangement: particles are close together and regularly packed

  movement: particles vibrate around a fixed point

  energy: particles have less kinetic energy than both liquids and gases

  
• liquids

  arrangement: particles are close together but irregular

  movement: particles are free to move

  energy: particles have less kinetic energy than gases but more than solids

  
• gas

  arrangement: particles are far apart and there are no forces between them

  movement: particles are free to move

  energy: particles have more kinetic energy than liquids and solids

  
• interconversions between states of matter:

  • melting
  • freezing
  • boiling
  • condensing
  • sublimation
• melting (solid to liquid)

  • when solid is heated, high kinetic energy makes particles vibrate fast enough so that forces of attraction between particles break
• freezing (liquid to solid)

  • when liquid is cooled, particles move slower and forces of attraction between them hold them together
• boiling (liquid to gas)

  • when liquid is heated, energy makes particles move fast enough so all forces of attraction are broken
• condensing (gas to liquid)

  • when gas is cooled, particles move slow enough so that some forces of attraction will hold them as a liquid
• sublimation (solid to gas)

  • very small number of substances can do this
  • when solid is heated, particles have more kinetic energy that breaks all forces of attraction
• diffusion: spreading out of particles in a fluid from an area of high concentration to an area of low concentration
• dilution of coloured solutions:

  • dissolving potassium manganate (VII) in water
  • diffusion of liquids is very slow because there are only small gaps between liquid particles into which other particles diffuse
  • random motion of particles causes purple colour to be spread evenly throughout water
  • more water causes potassium manganate (VII) particles to spread out further
  • makes it less purple
  • dilution

  
• diffusion experiments

  • ammonia (g) + hydrogen chloride (g) --> ammonium chloride (s) (white ring)
  • white ring of ammonium chloride forms closer to hydrochloric acid because ammonia particles are lighter, so they travel faster
  • takes about 5 minutes to form a white ring
  • particles move in random directions and will collide with air particles in tube

  
• solvent: a liquid that can dissolve other substances
• solute: a substance that is dissolved in a solvent
• solution: a mixture of two or more substances that are dissolved in each other
• saturated solution: when a solvent cannot dissolve any more substances because there are no more space between solvent particles
• element: substances that are made up of only one type of atom
• compound: substances that contain 2 or more elements chemically joined together in fixed proportions
• mixture: different substances in the same space, but not chemically combined
• pure substances have fixed melting and boiling points
• techniques for separation of mixtures:

  • simple distillation
  • fractional distillation
  • filtration
  • crystalisation
  • paper chromatograhy
• simple distillation

  • separates liquids from a solution
  • solution is heated in a flask
  • liquid evaporates
  • gas goes into a condenser (cooled by cold water)
  • gas comes out as liquid again in a beaker

  
• fractional distillation

  • separates a mixture of different liquids that have different boiling points
  • evaporates one liquid by keeping the bunsen burner at a certain temperature
  • gas goes into condenser
  • gas comes out as liquid again in a beaker

  
• filtration

  • separates an insoluble solid from liquid
  • mixture is poured into filter paper
  • solid does not pass through and is left behind (residue)
  • liquid passes through filter paper and is collected in a conical flask

  
• crystallisation

  • separates a dissolved solid from a solution
  • solution is heated, allowing solvent to evaporate, leaving a saturated solution behind
  • saturated solution is cooled slowly
  • crystals will begin to grow
  • crystals are collected by filtering the solution and dried

  
• paper chromatography

  • separates substances that have different solubilities in a given solvent (different coloured inks have been mixed to make black ink)
  • substances will travel up paper at different rates as they have different solubilities

  
• Rf value for paper chromatography

  • Rf = distance of dye from baseline/distance of solvent front from baseline