How do astronauts aboard the International Space Station drink water recycled from their own urine? Material processes - Separating mixtures - Separation by filtration Learning Points Filtration can be used to purify liquids. Filtration separates mixtures of solids and liquids or gases. A Twig Context Film. Reinforce and extend the learning required by the curriculum. Twig’s context films show abstract concepts in action in the real world.