Separating Mixtures

Separating Mixtures

• We separate mixtures using their physical properties.
• Size: Filtration
  • Furnace filter: Pulls large dust/particles from the air before pushing heat through your house.
  • Coffee filter: Catches large coffee bean pieces but allows very tiny pieces through to flavor the water and make coffee.
  • Cooking: We use sifters for flour to get rid of big chunks of flour. We pass cooked fruit through a cheesecloth to filter out the seeds and make smooth, seedless jams and jellies.
  • Archeologists: Use wire mesh screens called sives to get rid of small dirt particles and catch pieces of pottery, bones and other important things from where they are digging.
• Solubility: Separating a mixture by dissolving some of the mixture and then filtering out the rest.
  • First - Add a solvent (liquid) that one of the materials (soluble) will dissolve into and the others (insoluble) will not dissolve into.
  • Second - Filter the solution. The filter will catch insoluble materials while things that were soluble will pass through the filter with the liquid.
  • Last - Use use distillation or evaporation to separate the soluble dissolved material from the liquid.
• Boiling Point: Distillation
  • The material with the higher boiling point will vaporize into a gas, go through the tubing, then cool and condense back into a liquid on the other side.
  • The material with the lower boiling point will not vaporize and will stay put as a liquid.
  • Better than evaporation b/c you don't lose the liquid and you can separate two liquids.
  • Video: Separating Mixtures with Distillation 1
  • Video: Separating Mixtures with Distillation 2
• Density: Separating a mixture by making some substances sink and the others float.
  • Everything in the mixture you are separating this way should be insoluble! (not dissolve)
  • First - Pour the mixture of both substances into a liquid. The liquid should have a density higher than one substances and less than the other (the density of the liquid should be between the densities of both substances).
  • Second - Use a net or mesh to filter the substance with a density lower than the liquid (what is floating).
  • Last - Pour the remaining liquid and the substance with a density greater than the liquid (what sank) through a second filter to catch your substance and get rid of the liquid. (OR) Distill or evaporate the liquid out of the remaining substance.
• Melting Point: Separating mixtures by melting one then pouring it through a filter to catch what didn't melt
• Magnetism: Separates based on attraction to a magnet.
  • Materials made of iron, nickel, cobalt and some rare earth metals and special minerals are magnetic.