Year 5 were set a challenge: 

Sometimes separating mixtures and solutions have more than one step.  Imagine I have a container that holds rocks, iron, salt and sand. How can I separate them all into groups? 

The children had to use their scientific understanding to carefully and methodically use magnets, solutions, filtration, evaporation and dissolving to separate all the items. They showed their understanding of this with labelled diagrams.  It was a busy and loud lesson, where everyone was very pleased with their results!