O-Level Chemistry Filtration Practical: Residue, Filtrate and Safety

Filtration separates an insoluble solid from a liquid. In a supplied mixture of sand and salt solution, sand stays on the filter paper while dissolved salt passes through with the water. A clear filtrate is therefore not necessarily pure water.

This guide covers supervised gravity filtration of that room-temperature mixture. The trainer supplies the materials, protective equipment and waste instructions. Hot filtration, vacuum filtration and hazardous mixtures need different assessments. Read the general lab safety guide before assembling glassware.

Decide what you want to collect

The 2026 O-Level Chemistry syllabus, 6092, names filtration among practical techniques on page 27. The Royal Society of Chemistry sand-and-salt activity illustrates the separation principle. Its later heating step is outside this guide.

The retained solid is the residue; the collected liquid is the filtrate. Label their destinations before pouring. If the aim is to recover clean sand, an assigned wash can remove salt solution held between the grains. If the aim includes recovering dissolved salt later, keep the relevant filtrate and washings as instructed. Washing is a choice tied to the separation aim, not a universal final step for every solid.