How Sodium (Na) makes fire from water

Interesting fact: If you are a chemistry student and know the periodic table, you may have wondered why the chemical symbol for Sodium is Na. We found that it is likely named after the Natron Valley, following this explanation:

Salt (sodium chloride, NaCl) and soda (sodium carbonate, Na2CO3) had been known since prehistoric times, the former used as a flavouring and preservative, and the latter for glass manufacture. Salt came from seawater, while soda came from the Natron Valley in Egypt or from the ash of certain plants. Source: Sodium

So, the Na symbol for sodium is drawn from an Egyptian location where sodium carbonate was plentiful, the Natron Valley: One mystery solved.

As sodium does not occur as a single element in nature, sodium was not known as a metal until 1807.

Their composition [sodium chloride and sodium carbonate] was debated by early chemists and the solution finally came from the Royal Institution in London in October 1807 where Humphry Davy exposed caustic soda (sodium hydroxide, NaOH) to an electric current and obtained globules of sodium metal, just as he had previously done for potassium, although he needed to use a stronger current.

The following year, Louis-Josef Gay-Lussac and Louis-Jacques Thénard obtained sodium by heating to red heat a mixture of caustic soda and iron filings. Source: Sodium (above).

The phenomenon demonstrated in Thompson’s sodium experiment is explained in detail here.

For an article on the many uses of sodium, see Uses of sodium.

To bring the chemical element of sodium, which is a metal, into the realm of the ordinary, see this article which describes a way to make a chemical similar to sodium hydroxide, which is the equivalent of lye, used in soap making: Home-Made Sodium Hydroxide Substitute.

If you stop Grant Thompson’s video at about 38, you will see sodium granules floating in the liquid, which is labeled as lye, i.e., sodium hydroxide. Thompson, in his comments on the video, notes that no one to that point has commented on the sodium granules.

In the experiment shown by Thompson, he has started with pure sodium and illustrated how, in contact with water, it forms hydrogen gas, which is extremely flammable. Actually, it first forms sodium hydroxide, which then forms hydrogen gas, as clarified by Wikipedia:

Sodium hydroxide is also produced by combining pure sodium metal with water. The byproducts are hydrogen gas and heat, often resulting in a flame, making this a common demonstration of the reactivity of alkali metals in academic environments; however, it is not commercially viable, as the isolation of sodium metal is typically performed by reduction or electrolysis of sodium compounds including sodium hydroxide. Source: Wikipedia on Sodium hydroxide

So, we’ve experienced a bit of fun watching a process described by Thompson as “exothermic,” where elemental sodium contacting water forms sodium hydroxide, releasing hydrogen from water in the form of a flammable gas. It’s worth considering an extended definition of such a process:

exothermic: in thermodynamics, the term exothermic process (exo- : “outside”) describes a process or reaction that releases energy from the system, usually in the form of heat, but also in a form of light (e.g. a spark, flame, or flash), electricity (e.g. a battery), or sound (e.g. explosion heard when burning hydrogen).

Source: Exothermic Process