When a chunk of palladium metal is ground into a very fine powder and heated to drive off any atmospheric moisture, the surface area of the metal increases dramatically. This causes the metal to become more reactive, and it can easily react with oxygen in the air to form palladium oxide. This reaction is exothermic, meaning that it releases heat. The heat can cause the palladium oxide to decompose, releasing oxygen gas and leaving behind palladium metal. This process is known as the Ostwald process, and it is used to produce palladium metal powder for use in a variety of applications, including catalysis, fuel cells, and jewellery.