Thank you for your question. Sodium can be used in secondary schools in Australia as a teacher demonstration of the reactivity of alkaline metals. It is an exciting, memorable and engaging demonstration for students that can be performed safely with the appropriate procedures in place.
NB. Sodium has a DG Class: 4.3, Hazard symbols: Dangerous When Wet and Corrosive. Refer to current SDS for Risk and Safety Statements.
Sodium metal reacts rapidly with water forming a colourless solution of sodium hydroxide (NaOH) and Hydrogen gas (H2). The resulting solution is basic because of the hydroxide, which can be illustrated by using a few drops of phenolphthalein in the water. The sodium will leave a pink trail behind it as it reacts. The reaction is: 2Na(s) + 2 H2O –> 2Na+ + 2 OH- + H2 (g)
The reaction is highly exothermic. During the reaction, the sodium may catch fire, may spray out molten sodium metal and the hydrogen gas may ignite, so it is imperative that proper safety precautions be used when conducting this demonstration. The demonstration should be undertaken by trained personnel in conjunction with a current safety data sheet (SDS) and a site-specific risk assessment.
- To protect observers, the reaction can be carried out behind a Perspex safety screen with students at a safe distance away.
- PPE (i.e., gloves and safety glasses) should be worn. Sodium metal causes severe burns on eye or skin contact.
- While wearing gloves, use a dry spatula or scalpel blade to remove a rice-grain-sized piece of sodium (3mm3) from pieces stored in oil by cutting on a dry clean surface such as a glass petri dish. Whilst cutting, quickly point out that the shiny sodium metal surface rapidly darkens due to reaction with air and moisture.
- Return the unused sodium to the oil and seal the container. Sodium needs to be stored under liquid paraffin or kerosene to prevent a reaction with oxygen or water vapour.
- Use a thick glass pneumatic trough or large Pyrex beaker filled with water to within 1cm of the top so there is minimal space for the air/hydrogen mixture to accumulate.
- Use tongs or tweezers to drop the piece of sodium into the water.
- Use wire gauze to cover the beaker or trough during the reaction to stop pieces of sodium from escaping.
- After the sodium has reacted completely, the petri dish, scalpel and tweezers should be placed in the water in the beaker or trough to make sure there is no residual sodium left.
- The remaining hydroxide solution can be flushed away with water down the drain. Continue to wear eye protection and PPC when disposing of the reaction.