What is the law of conservation of mass?

The law of conservation of mass is a fundamental principle in science stating that mass cannot be created or destroyed in a closed system through ordinary chemical or physical processes. In other words, the total mass of substances involved in a chemical reaction or physical change remains constant, even though the substances themselves may change form or combine differently. This law was first formulated by Antoine Lavoisier in the 18th century and is a cornerstone of chemistry and physics. For example, when you burn wood, the mass of the wood and oxygen before burning equals the mass of the ash, gases, and other products after burning, assuming you capture all the products. This principle helps scientists balance chemical equations and understand how matter behaves in reactions. In summary, the law of conservation of mass assures us that matter is neither lost nor gained during chemical reactions; it simply changes from one form to another, maintaining the total mass constant.