If you spill an acid or alkali onto your hand, you must remove it using water. You must never try to neutralise it Can you see why? Neutralisation is an exothermic reaction and can produce enough heat to burn your hand. Adding water to the acid also produces heat, though much less than in neutralisation.
Metal Displacement Reactions
For example, when zinc reacts with copper(II) sulfate solution in a test tube, the reaction gives out heat and the test tube becomes warm.