topic two states of matter and mixtures

• changes in state

  • the arrangement and movement of particles change during transitions between states. need to refer to;
  • distance between particles
  • speed of particles change
  • the kinetic energy (KE) the particles has changes
  • the strength of the attractive forces between particles changes
  • solid --> liquid (melting) --> gas (boiling/evaporation)
  • gas --> liquid (condensation)-->solid (freezing)
  • solid --> gas ( sublimation)
  • gas --> solid (deposition)
• cooling/ heating curves

  • the horizontal sections, where the temperature remains constant representing the changes in state
• heating curve with pure substance / impure substance

  • pure substance has smooth curve indicating time clearly
  • impure substances the melting point is not a defined temperature but over a range of temperatures
• key words

  • mixture = a substance containing two or more different subtance that are not chemically joined together
  • compund = substance made of more than one type of element chemically bonded together
  • element = a simple substance consisting of only one type of atom
  • pure substance = has the same fixed composition in all parts and so we cant separate itinto other substances using physical methods.
• separation techniques - filtration

  • filtration - using a filter to separate insoulable substances from a liquid
  • filtrate - a solution that has pssed through a filter
  • insouble - a substance that cannot be dissolved in a liquid
  • the filtered soiled that remains on the filter paper is known as the RESIDUE
  • crystallisation - solutes can be separated from the solution by evaporating the solvent to leave the solute behind
• separation techniques - filtration - risks

  • crystallisation, risk of spitting from the evapourating basin
  • reduced by wearing eye protection, removing the bunsen burner before solution is completely dry , or using steam to heat the evaporating basin gently
• the particle model

  • solids - arranged in a regular pattern, close togther - vibrate on the spot
  • liquids - random arrangemnt, close togther
  • gas - arranged far apart in random arrangement - moves quickly in all directions
• chromatography - method

  1. draw pencil line on paper , 2 cm above bottom
  2. add dots of ink on line
  3. place paper in container of water , not slumped, allow water to travel through paper
  4. take paper out before reaching to top and mark where solvent traveled to
  5. measure the distance travelled by water from pencil line to each substance
  6. calculate rf value (distance traveled by solute/ distance travelled by solvent)
• distillation

  • distillation the process of seperating a liquid from a mixture by evaporating the liquid then condensting it so it can be collected
• simple distillation of ink -method

  1. wear eye protection
  2. set up apparatus , ink is in flask, and vapours can be led away to be condesnsed 
  3. heat flask of ink using bunsen burner , making ink simmers gently , does not boil to delivery tube
  4. continue heating until you have collected a few cm^3 of distillate ( distilled solvent )
  5. note max temperature obtained
• purification of drinking water


  • fresh water contains : objects such as leave and twigs , insoluble particles , soluble particles , bacteria
  • steps of purification of drinking water
  • screening using sieve , sedimentation ( allowing small particles to settle at the bottom ) , filtration , chlorination to kill bacteria