“Jumping sodium” experiment
Ноw to make sodium jump
An experienced chemist can synthesize a substance, carry out a reaction, and… make sodium “jump”! In this experiment we will look at one of the main properties of alkaline metals – the reaction with water.
Reagents and equipment:
- water (60 ml);
- kerosene (40 ml);
- 1% solution of thymolphthalein;
- metallic sodium;
- 2 measuring vessels.
- Pour 30 ml of water into each measuring cylinder.
- Add a few drops of the solutions of the thymolphthalein and phenolphthalein indicators to the water.
- Pour 20 ml of kerosene into each measuring cylinder. Two layers form of liquids that do not mix.
- Cut a piece of metallic sodium and add it to each vessel.
First the sodium passes through the layer of kerosene, with which it does not react. When the sodium contacts the layer of water, a violent reaction takes place with the release of gas and gradual coloring of the lower layer of liquid. The piece of sodium begins to jump constantly because of the gas released.
Kerosene and water have different density and do not mix together. Sodium does not react with kerosene, but reacts with water, forming an alkali (sodium hydroxide) and hydrogen:
2Na + 2H₂O = 2NaOH + H₂
Gas bubbles push the sodium into the layer of kerosene, but due to the force of gravity the sodium sinks back to the layer of water. Thus, sodium seems to jump in the layer of kerosene! It will jump like this until it has reacted completely with the water.
Sodium hydroxide, which forms in the reaction, changes the acidity of the medium of the lower layer of liquid. The indicators react to this change, turning the lower layer a certain color. Thymolphthalein turns blue, and phenolphthalein turns deep pink.
This experiment must be carried out in protective gloves and glasses, observing safety rules in working with flammable substances. Metallic sodium ignites on contact with water, so it is stored in jars with thick glass walls under a layer of kerosene. The unreacted remains of sodium must be destroyed by dissolving them in ethanol. They must not be flushed down the drain.
Warning! Don’t try to repeat this experiment without a professional supervision!