atoms, elements, compounds and mixtures

• what is a compound?

  2 or more atoms chemically combined in fixed proportions
• what is a mixture?

  2 or more elements that aren't chemically combined
• what is filtration used for?

  to separate liquids from insoluble solids
• what is crystallisation used for?

  to obtain a soluble solid from a solution
• what is simple distillation used for?

  to obtain a solvent from a solution
• what is fractional distillation used for?

  to separate mixtures in which the components have different boiling points
• what is chromatography used for?

  to separate the different soluble and often coloured components of a mixture
• name 5 ways of separating mixtures?

  • filtration
  • crystallisation
  • simple distillation
  • fractional distillation
  • chromatography