chemistry igcse edexcel

• how are solid particles arranged?

  close together and regularly packed
• how do solid particles move?

  vibrate around a fixed point
• how are the particles in a liquid arranged?

  close together but irregular
• how do particles in a liquid move?

  move around each other
• how are particles in a gas arranged?

  far apart with no forces between them
• how do gas particles move?

  quickly and randomly in all directions
• what state has the most energy?

  gas
• describe this: solid - liquid

  when a solid is heated, the energy makes the particles vibrate faster so the forces of attraction break known as melting
• describe this: liquid - solid

  when a liquid is cooled, the particles move slow enough so that the forces of attraction hold them into place known as freezing
• describe this: liquid - gas

  when liquid is heated strongly, the energy makes the particles move fast enough so the forces of attraction break known as boiling
• describe this: gas - liquid

  when gas is cooled, the particles move slow enough so the forces of attraction hold known as condensing
• what is a solute?

  substance which dissolves
• what is a solvent?

  the liquid in which the solute dissolves
• what is a solution?

  the liquid formed from the solute and solvent
• what is a saturated solution?

  a solution into which no more solute can dissolve
• what does dissolving potassium manganate in water demonstrate?

  diffusion in liquids is very slow as there are only small gaps between the particles for other particles to diffuse into
• explain how dilution is shown through the experiment using potassium manganate

  the random motion of particles cause the purple colour to evenly spread in the water and adding more water to the solution causes the potassium manganate particles to spread out further so the solution becomes less purple
• what reacts to form ammonium chloride?

  ammonia gas and hydrogen chloride
• what is the word equation for this reaction?

  ammonia + hydrogen chloride -> ammonium chloride
• what is an element?

  the simplest type of substances made up of only one type of atom
• what is a compound?

  a substance that contains two or more elements chemically joined together
• what is a mixture?

  a combination of two or more substances that are not chemically bonded
• what is the difference between a pure substance and a mixture?

  pure substances melt and boil at fixed temperatures whereas mixtures melt and boil over a range of temperatures because they consist of different substances
• what is the separation technique ‘simple distillation’ used to separate?

  a liquid and soluble solid from a solution
• what is an example?

  water from salt water
• what is the method for simple distillation?

  1. solution is heated and water evaporates which forms vapour
  2. vapour rises and passes through condenser where it cools and condenses
  3. this turns it into the pure liquid that is collected in a beaker
  4. after all water is evaporated only the solid will be left behind
• what is ’fractional distillation‘ used to separate?

  a mixture of liquids that are miscible with one another
• give an example

  ethanol and water
• what is the method for fractional distillation?

  1. solution is heated to the temp of the substance with the lowest boiling point (ethanol 78*)
  2. this substance will evaporate and vapours will pass through condenser where they cool and condense turning into a liquid that will be collected in beaker
  3. all of the substance is evaporated and collected leaving behind other component
• what is filtration used to separate?

  an undissolved solid from a mixture of solid and liquid
• give an example

  sand from sand water
• what is the method for filtration?

  1. filter paper is placed in funnel above beaker
  2. mixture is poured into funnel
  3. the filter will only allow small liquid particles to pass through as filtrate
  4. solid particles are too large so are collected in filter paper
• what is crystallisation used to separate?

  dissolved solid from a solution when solid is more soluble in hot solvent than in cold
• give an example

  copper sulfate from copper sulfate in water
• what is the method for crystallisation?

  1. solution is heated and solvent evaporates leaving saturated solution
  2. to test if solution is saturated, dip clean glass rod into solution and crystals should form on rod
  3. leave to cool and crystallise
  4. crystallise are collected by filtering the solution, they are washed with distilled water and left to dry
• what is paper chromatography?

  a technique used to separate substances that have different solubilities
• Paper chromatography method

  1. Draw a pencil line on chromatography paper

  2. Place spots of the sample on the pencil line

  3. Lower the paper into the solvent container, ensuring the pencil line sits above the solvent level

  4. Solvent travels up the paper by capillary action, taking some of the coloured substances with it

  5. Substances with higher solubility will travel further than others
• Stationary phase

  The paper
• Mobile phase

  The solvent
• Pencil is used instead of ink as ink would run into the chromatogram along with the samples