When potassium permanganate (KMnO4) is dissolved in water, it forms a deep purple solution. However, when this solution is heated, the color changes. The purple color fades and the solution becomes a pale pink color. This is because the heat causes the permanganate ions (MnO4-) to decompose, releasing oxygen gas and forming manganate ions (MnO4(2-)). The manganate ions are responsible for the pink color of the solution.

The chemical reaction that takes place when potassium permanganate is heated in water can be represented as follows:

2KMnO4(aq) + heat → 2MnO4(2-) (aq) + O2(g) + 2K+ (aq)

The heat causes the permanganate ions to break down into manganate ions, oxygen gas, and potassium ions. The manganate ions give the solution a pink color, while the oxygen gas bubbles out of the solution.