How can you make crystals?

• A. Heat to the point of crystallisation, leave to cool gradually, filter, dry and collect the crystals
• B. Add more solvent and heat until all crystals form
• C. Cool the solution rapidly and filter immediately
• D. Stir vigorously until crystals disappear

Answer: (A)

Crystallisation happens when a saturated solution loses solvent or cools, so dissolved particles come out of solution and arrange into a regular lattice. To make crystals, dissolve the substance in a hot solvent until the solution is saturated, then let it cool slowly (or allow evaporation) so crystals can grow. After formation, filter to separate the crystals from the liquid and dry them to remove solvent. The other approaches either keep the substance dissolved, produce tiny or impure crystals with rapid cooling, or disturb crystal formation.