Oxygen gas carbon dioxide The most abundant element on Earth is oxygen (chemical symbol O), and it is essential to all the planet's life forms. As the gas O2 it is in the lower atmosphere in the air that is breathed Animals breathe out carbon dioxide, and plants take in carbon dioxide to make nutrients that all organisms need, to make oxygen for animals to breathe. Water Ammonia Aside from drinking, water is used for cooking, cleaning, recreation (e.g. swimming pools), and keeping plants alive. Ammonia is also used as a refrigerant gas, for purification of water supplies, and in the manufacture of plastics, explosives, textiles, pesticides, dyes and other chemicals. It is found in many household and industrial-strength cleaning solutions. Methane Sodium chloride (salt) Methane traps heat in the atmosphere. Methane is also the main ingredient in natural gas. Because methane can be captured from landfills, it can be burned to produce electricity, heat buildings, or power garbage trucks. More commonly referred to as “salt” or “table salt,” sodium chloride is used as a seasoning in many foods. Medically, sodium chloride solutions are used in catheter flush injections or intravenous infusions, and for cleaning objects such as contact lenses in the form of saline Diamond