Reactive metals in A-level practicals mainly include alkali metals (Group 1: lithium, sodium, potassium) and Group 2 metals (magnesium, calcium). These are highly reactive with water (producing flammable hydrogen gas and heat) and air (forming oxides/hydroxides). They are flammable and can cause severe burns or fires if mishandled.
1. Storage Methods
• Alkali metals (Li, Na, K): Store under liquid paraffin (mineral oil) in a sealed, labelled glass jar. Ensure the metal is fully submerged at all times — check levels regularly.
- Potassium needs extra checks: Look for a “custard yellow” superoxide coating (shock-sensitive and explosive). If seen, dispose of the sample safely — do not use.
- Keep stocks minimal and in a secure, locked location
• Group 2 metals (Mg, Ca): Store in a cool, dry place. Magnesium powder/turnings are especially flammable; control stocks carefully to prevent theft or misuse. No oil required but keep away from moisture.
• General: Store away from water, acids, and oxidisers. Use a dedicated “flammable water-reactive metals” container if available. Never store in a sand bath (it can hide leaks).
2. Handling Procedures
• Never touch with bare hands — always use forceps or tweezers.
• Cut pieces only when needed and under dry conditions (technician usually pre-cuts small pieces: Li ≈5 mm cubes, Na ≈4 mm cubes, K ≈3 mm cubes).
• Work on a dry tile or in a trough. For demos, use the smallest possible piece.
• After use: React any residues safely with ethanol (for Li/Na) or 2-methylpropan-2-ol (for K) until fizzing stops, then dilute with water. Place used apparatus in a water trough immediately.• Magnesium ribbon/turnings: Handle with tongs; powder is self-heating in bulk.
• Calcium: Reacts with moisture to form corrosive oxide/hydroxide — keep dry.
3. PPE Requirements
• Eye protection (safety goggles or spectacles) must be worn at all times by everyone in the lab — alkali metals and burning magnesium can spit or produce bright flames that damage eyes.
• Lab coat (buttoned up) and closed-toe shoes.
• For the demonstrator: Use a safety screen in front of the apparatus.
• For magnesium burning: View only through shade 9 welding filter (never look directly at the flame).
• Additional: Gloves are not normally required for small-scale work (forceps are used), but chemical-resistant gloves may be needed when cleaning up spills.
4. Reaction Demonstrations (Common A-Level Practical Examples)
All demos are teacher-only (or highly supervised) and use tiny pieces in a water trough or spotting tile for visibility (often projected).
• Alkali metals with water (classic reactivity trend: Li < Na < K): Small piece dropped into water trough containing universal indicator. Observe fizzing → floating/melting (Na, K) → flame (K especially) → alkaline solution. Equation: 2M(s) + 2H₂O(l) → 2MOH(aq) + H₂(g). Safety: Safety screen, eye protection, dry conditions, sand ready.
• Group 2 with water/acids: Calcium reacts vigorously with water (hydrogen + heat). Magnesium ribbon reacts slowly with cold water but vigorously with acid (H₂ gas). Use for displacement reactions (e.g., Mg in CuSO₄ solution) to build the reactivity series.
• Magnesium burning in air: Short ribbon or powder; burns with intense white flame. Never look directly — use welding filter. Extinguish only with dry sand (not water/CO₂).
• Displacement reactions (e.g., metals in salt solutions on spotting tiles): Small scale, low risk, excellent for comparing reactivity.
Preparation tip: Technician pre-cuts and stores small pieces in oil. Demo takes 10–20 minutes. Always describe observations before explaining chemistry.
5. General Safety Tips & Emergency Procedures
• Risk controls (CLEAPSS “typical control measures”):
- Small scale only.
- Dry conditions everywhere.
- Safety screen + eye protection.
- Everyone (including technicians) must understand the hazards.
- Keep a container of clean, dry sand ready at all times (for metal fires — never use water, foam, or CO₂ on burning alkali metals).
- No flames near magnesium. Keep students back.
• Fire: Smother with dry sand. Alert teacher immediately.
- Remove solid pieces with forceps.
- Irrigate with copious running water for at least 20 minutes.
- Seek medical help (999/111 if large area or symptoms).
• Eye contact: Use eyewash station and go hospital if needed.
• Swallowed: Rinse mouth only — do not induce vomiting.
Follow these guidelines and you’ll stay safe while getting great results from your reactivity series practicals. Your school’s CLEAPSS resources or teacher will have the exact Hazcards for your specific metals — refer to them before every session.
Stay safe and enjoy the demos!