Nitrogen is often referred to as an inert gas and is used in some inert atmospheres for metal processing and in light bulbs to prevent arcing, but it is not chemically inert. It is an essential element in animal and plant life and is a component of many useful compounds. Nitrogen combines with many metals to form hard nitrides, which can be used as wear-resistant metals. Small amounts of nitrogen in steel inhibit grain growth at high temperatures and also increase the strength of some steels. It can also be used to create hard surfaces on steel. Nitrogen gas can be used to make ammonia, nitric acid, nitrates, cyanide, etc.; in making explosives; filling high temperature thermometers, incandescent light bulbs; forming an inert material to preserve materials, used in dry boxes or glove bags. Liquid nitrogen during food freezing; as a coolant in laboratories.