A process in which molecular bonds break or form between electron-sharing atoms or molecules to create substances with new properties or characteristics. For example, oxygen and hydrogen combine to form water. Sodium (a metal) and chlorine (a gas) combine to form sodium chloride, or common salt. Glucose (C6H10O5) is metabolized to carbon dioxide (C02) and water (H20). Oxygen combines with hemoglobin to form oxyhemoglobin when the hemoglobin in the blood comes into contact with the oxygen in the air contained in the alveoli of the lungs. A chemical change is also known as a chemical reaction.
A change in the chemical composition or make-up of a substance.