Why do water drops form on cold windows and why does water freeze? Material processes - Solids, liquids and gases - Changes of state Learning Points Condensation is the change of state from gas to liquid. Freezing is the change of state from liquid to solid. Liquid water freezes at 0°C. A Twig Curriculum Film. Delivering key learning points. Get straight to the facts in just three minutes – directly linked to core learning, Twig's curriculum films will fit neatly into your lesson plans.