Suggest suitable separation and purification techniques, given information about the substances involved

🔬 In chemistry we often have a mixture of substances that we want to split apart or clean up. Think of a coffee filter that lets the liquid through but keeps the grounds behind it. In the lab we use a range of “filters” and “sieve‑like” techniques to separate and purify.

• 🧪 Filtration – separates solids from liquids using a filter paper. Example: removing sand from a salt solution.
• 💧 Decantation – carefully pouring off the liquid from a settled solid. Think of pouring water out of a glass of muddy water.
• 🌬️ Evaporation – leaving a solid behind by heating a liquid to boil away the solvent. Example: drying a salt solution to get back the salt.
• 🔄 Distillation – uses boiling points to separate liquids. Like separating alcohol from water by heating.
• 🧪 Chromatography – uses a stationary phase and a mobile phase to separate components. Imagine a paper towel moving up a slide with ink spots spreading out.
• 🌀 Centrifugation – spins a mixture to push heavier particles to the bottom. Like spinning a salad to get the dressing out.

• 🧪 Recrystallisation – dissolving a solid in hot solvent, then cooling to form pure crystals. Like making sugar crystals from a sugary solution.
• 🌬️ Sublimation – solid turns directly to gas and re‑solidifies elsewhere. Think of dry ice turning into CO₂ gas.
• 🔄 Distillation (again) – can be used to purify a liquid by removing impurities with different boiling points.
• 🧪 Chromatography – also purifies by separating components on a column or paper.

💡 When deciding which method to use, ask yourself:

1. Is the mixture solid‑liquid or liquid‑liquid?
2. What are the boiling points or solubilities of the components?
3. Do we need a pure product or just a separated mixture?
4. What equipment is available in the lab?

Example: If you have a mixture of salt (NaCl) and sand, filtration works because salt is soluble in water while sand is not.

Example: If you have a mixture of ethanol (C₂H??

OH) and water (H₂O), distillation is best because their boiling points differ (ethanol 78 °C vs water 100 °C).

📝 Remember to:

• State the principle behind the technique (e.g., “filtration separates solids from liquids based on particle size”).
• Explain why the chosen technique is appropriate for the substances (e.g., solubility, boiling point, polarity).
• Use correct chemical notation (e.g., \$C6H{12}O_6\$ for glucose).
• Show a clear diagram or flowchart if required.