What is the second step in making crystals?

• A. Leave to cool gradually.
• B. Heat to crystallisation.
• C. Filter, dry and collect the crystals.
• D. Stir the solution.

Answer: (A)

The main idea here is how crystals form from a dissolved substance. When you heat a solution you move toward dissolving as much of the substance as possible, creating a hot, saturated solution. The second step is to let that solution cool gradually. As the temperature drops, the solubility decreases, so the dissolved substance starts to come out of the solution and form crystals. Cooling slowly gives time for the particles to arrange into well-formed crystals, often larger and fewer in number, rather than many tiny ones that might form with rapid cooling or stirring.

After this cooling step, you would typically filter, dry, and collect the crystals. Stirring or heating again would disrupt the delicate process of crystal growth, so cooling gradually is the right move for the second step.