Carbon dioxide is a molecule composed of one carbon atom bonded to two oxygen atoms. Carbon dioxide is usually a gas and it is a gas at room temperature. It is exhaled by animals and humans and used by plants to produce oxygen and in solid form it is dry ice. The chemical formula for carbon dioxide is CO2 and is a colorless, odorless, tasteless, non flammable gas. Carbon dioxide makes up one of the gases in our atmosphere. In the atmosphere, carbon dioxide is a greenhouse gas. We use carbon dioxide to make drinks fizzy and keep foods fresh. The amount of carbon dioxide in the atmosphere is maintained through a balance.