GCSE Combined Science (AQA)

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Crystallisation

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Atomic structure and the periodic table A simple model of the atom, symbols, relative atomic mass, electronic charge and isotopes

Crystallisation

4:02 Separation of Mixtures
Spec 4.1.1.2
Previous Filtration Next Simple Distillation
  • Crystallization is a process used to separate mixtures, specifically a dissolved substance from a solvent.
  • Example setup: separating copper sulfate from water using a crystallization dish.
  • During crystallization, water evaporates, leaving solid copper sulfate crystals.
  • Crystallization is a physical process, not involving a chemical reaction, and no new substances are made.
  • The process involves changing the physical state of substances, not their chemical composition.
  • Step-by-step process:
  • Step 1: Pour solution into an evaporating basin and gently heat to evaporate the solvent.
  • Use a wide, flat evaporating basin for better evaporation.
  • Heat the solution gently with a bunsen burner.
  • Step 2: As the solvent evaporates, crystals begin to form.
  • The solution becomes more concentrated as water evaporates.
  • Crystals form, and their color depends on the dissolved solid.
  • Turn off the bunsen burner when water level is low to avoid damaging crystals.
  • Remaining solvent evaporates slowly, leaving only crystals.
  • Step 3: Once solvent evaporates, dry crystals by patting with filter paper.
  • Scrape crystals out of the basin and pat dry to remove remaining solvent.
  • Final product: dry crystals.

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