What happens when you heat potassium permanganate?
It makes oxygen.
"Reaction with what other substance? It needs something to react with." Yes, it depends with what it is reacting.....but permanganate is a oxidative reagent, so it could possible oxidate others reagents, like carbon double bonds or triple bonds....if it is acidic solution, it´s more oxidant....it can break bonds and oxidate organic compounds.....it I think that the question is what happens when potassium permanganate (manganate VII) is heated. potassium permanganate + heat= potassium oxide + oxygen