I Didn’t Know That...

Q. Why does a gas stove burn yellow when a pot of boiling water overflows?

A. Because of sodium ions in the water in the form of sodium chloride or salt. Most tap water contains small amounts of salt, and many people add salt to boiling water. When the sodium ions are heated, they give off a yellow light. Incidentally, the white crystals left behind when the pot boils over are also primarily sodium chloride.