elements, compounds and mixtures

• atoms are


  the smallest particles that makes matter which contains subatomic particles electrons, protons, and neutrons
• atoms combine to forms elements, compounds and mixtures
• elements are 


  Substances made up of only one type of atom.
• • There are more than 100 different elements having different properties
• elements can be metals, non-metals or semi metals
• • Periodic table represents all the known elements in the order of increasing proton number
• mixtures are


   substances made up of two different elements or compounds which are not combined chemically.
• In mixtures the mixed components retain their properties and can be separated by physical means

  Oil and Water

  • eq: Salt and water
  • Sand and Water
  • Oil and Water
• compounds are


  substances which have more than one atom chemically bonded.
• filtration separates


  an insoluble solid from a liquid

  e.g sand and water
• crystallisation separates


  a soluble solid from a liquid

  e.g salt and water
• distillation separates

  soluble liquid or solid from liquid

  eg oil or sand and water
• fractional distillation separates


  a mixture of liquids with similar boiling points
• filtration

  • Solid component can be separated from a liquid using this technique.
  • Solution runs off with soluble components and insoluble component like Sand stick to the filter paper as residue.
  • The run off is the filtrate which can be water or the solution with the dissolved components
• crystallisation

  • Heating the mixture in an evaporating basin or water bath
  • Water will evaporate leaving the crystals of solids behind.
  • Solid can then be collected on a filter paper and dried.
• distillation

  • It can be used to separate solid and a liquid in which solid is completely soluble in the solvent.
  • It can also be used to separate two liquids which are completely miscible in each other and have different boiling points.
  • In evaporation solvent is allowed to evaporate leaving solid behind but in distillation solvent is evaporated and the vapours are passed on to the condenser which cools the vapour and collect the solvent in a separate container.
  • In case of separation of two liquids, the one with the lower boiling point will evaporate first and will be collected by the condenser.
• What is fractional distillation used for?

  To separate liquids with similar boiling points
• Why can't distillation effectively separate liquids with similar boiling points?

  Because their boiling points are too close
• What type of flask is used in fractional distillation?

  Round bottom flask
• What is the purpose of the tall fractionating column in fractional distillation?

  To enhance separation of liquid mixtures
• What are the glass beads in the fractionating column used for?

  To provide surface area for condensation
• How do vapors behave in the fractionating column?

  They evaporate and hit the glass beads
• What happens to lower boiling point liquids in the fractionating column?

  They travel high up and reach the condenser
• What occurs to high boiling point liquids in the fractionating column?

  They hit the glass beads and condense
• Where do high boiling point liquids go after hitting the glass beads?

  They go back to the flask
• What is the process of fractional distillation?

  • Used to separate liquids with similar boiling points
  • Round bottom flask with fractionating column and condenser
  • Vapors evaporate, hit glass beads
  • Lower boiling liquids rise, reach condenser
  • High boiling liquids condense, return to flask
• chromatography

  • Components in the mixture are separated on the basis of solubilties of different components of the mixture in a suitable solvent.
  • A capillary tube is used to spot the mixture on the chromatography paper.
  • The paper is put inside a solvent and the solvent is allowed to run up the chromatography paper.
  • The component of the mixture which is more soluble in the solvent will travel greater distance and will leave its mark near the top.
  • The component which is less soluble will have a mark near the bottom.