Nigel Baldwin | Potassium in water reaction MVI 1348 @nigelbaldwin3184 | Uploaded March 2018 | Updated October 2024, 1 hour ago.
Potassium and water reaction

High School Chemistry

The reaction of potassium metal with water.

A small piece of potassium metal, approx. 0.3cm diameter, is dropped into a beaker of water.

The potassium reacts violently.

Observations:
1 The potassium floats, potassium is less dense than water.
2 Potassium reacts explosively; it bursts into flames with a lilac colour.
Initially, residues of petroleum-ether used to clean the mineral oil in which the potassium was stored are burnt off giving a yellow-orange fire which is quickly replaced by lilac flame of the burning potassium metal.
Hydrogen gas is also propduced and contributes to the size of the flame.
3 The potassium melts into a ball with the heat of the reaction, seen most prominently at the end of the movie where an orange ball of molten metal is seen moving rapidly across the surface of the water.

potassium + water = potassium hydroxide + hydrogen

In this case, Universal Indicator was not added to the water, which is usually done to show the production of the alkali potassium hydroxide.