GCSE Chemistry

• Purity


  something that only contains one compound or element throughout
• boiling point


  a chemically pure substance will melt or boil at a specific temperature - you can test for a substances purity by comparing it with the boiling point of that pure substance
• Formulations


  useful mixtures with a precise purpose - each component is measured exactly and contributes to the properties of the formulation
• formulation of paint

  pigment, solvent, binder, additives
• Paper chromatography


  mobile phase = where the molecules can move, this is always a liquid or a gas

  stationary phase = where the molecules can't move - a solid or thick liquid
• mobile phase


  the chemical that spends more time in the mobile phase will move further through the stationary phase
• high solubility molecules


  will spend more time in the mobile phase
• Rf Value


  distance travelled by substance/distance travelled by solvent
• test for chlorine


  chlorine turns damp litmus paper white
• test for oxygen

  relight a glowing splint
• test for carbon dioxide

  when bubbled through lime water it will turn it cloudy
• test for carbonates

  adding dilute acid, then bubble the gas that is given off through lime water - if it is a carbonate the gas will be carbon dioxide
• test for sulphates

  using a pipette add a few drops of dilute hydrochloric acid then some barium chloride solution

  if a sulphate is present, a white precipitate will form= bariumsulfate
• test for halides


  to identify a halide ion, add dilute nitric acid then silver nitrate solution

  a chloride = white precipitate = silver chloride

  a bromide - cream precipitate = silver bromide

  a iodide = yellow precipitate = silver iodide
• lithium


  crimson flame
• sodium

  yellow flame
• potassium


  lilac flame
• calcium

  orange red flame
• copper


  green flame
• Metals with sodium hydroxide

  calcium = white

  Copper = blue

  Iron II = Green

  Iron III = Brown

  Aluminium = white (dissolves in excess - colourless)

  Magnesium - white