Filtration and Crystallisation

Question 1

filtration

Answer 1

• used to separate an insoluble solid from a liquid
• it can also be used in purification
• method = put filter paper into a funnel and pour in the mixture
• the liquid part of the mixture will run through the paper, leaving behind a solid residue

Question 2

crystallisation

Answer 2

• separates a soluble solid from a solution
  method:
  1. pour solution into an evaporating dish and gently heat - some of the water will evaporate and the solution will get more concentrated
  2. once some of the water has evaporated or when crystals start to form (point of crystalisation), remove the dish from heat and leave the solution to cool
  3. the salt should start to form crystal as it becomes insoluble in the cold, highly concentrated solution
  4. filter the crystals out of the solution and leave them in a warm place to dry - could also use a drying oven or a desiccator

Question 3

how to use filtration and crystallisation to separate rock salt

Answer 3

• rock salt is a mixture of salt and sand - these are both compound, however salt dissolves in water and sand doesn’t
  method:
  1. grind up the rock salt with a pestle and mortar
  2. dissolve in beaker and stir
  3. filter through filter paper in a funnel
  4. evaporate in an evaporating dish
• the sand is insoluble so it stays as big grains and collects on the filter paper
• the salt dissolves in the solution, and when the water is evaporated, the salt forms as crystals in the evaporating dish