Chemistry, 2: Experimental techniques

• What do you use to measure time?

  Stopclock
• What do you use to measure temperature?

  Thermometer
• What do you use to measure mass?

  Balance or scale
• What do you use to measure volume of liquids?

  Burettes

  Pipette

  Measuring cylinder
• How do you go about paper chromatography?

  Separating solutions or liquids that are mixed together

  Draw a line with graphite as it is insoluble
• How do you find the retention factor?

  Compare distances that substance has travelled up the filter paper with distance travelled by solvent

  Solvent will always travel further than substance, so Rf is always <1
• To find purity of substance, use heat to find temperature at which substance melts or boils
• Impure solids have a lower melting point than pure solid
• Liquids containing solutes will have a higher boiling point than pure liquid
• How do you purify impure solids?

  1. Add solvent that solid is soluble in to dissolve it
  2. Filter the mixture to remove insoluble impurity
  3. Heat the solution to remove some solvent and leave to crystallise
  4. Filter off crystals, wash off with cold solvent and dry
• When do you use distillation?

  Liquids that are contaminated with soluble solids dissolved in them
• How do you distill impure liquids?

  1. Heat solution
  2. As solvent boils, it turns into vapour
  3. Solvent condenses back into pure liquid and is collected in beaker
• Distillation is used in desalination plants, which produces pure drinking water from sea water
• When do you use fractional distillation?


  For liquids contaminated with other liquids
• How do you use fractional distillation?

  1. Boil mixture
  2. Liquid with lowest boiling point turns into vapour firsts, condenses and is collected
  3. Fractionating column increases purity of distilled product by reducing amount of other substances in the vapour when it condenses