Which principle states that matter is neither created nor destroyed during a chemical reaction?

The principle that states matter is neither created nor destroyed during a chemical reaction is known as the Conservation of Mass. This fundamental concept implies that in any closed system, the total mass of the reactants before a reaction will equal the total mass of the products after the reaction. This principle is crucial in balancing chemical equations, where the number and type of atoms remain constant throughout the reaction, ensuring that all mass is accounted for.

This principle was first clearly articulated by Antoine Lavoisier in the late 18th century and is a cornerstone of chemical science. It emphasizes that even though substances may change their forms and properties during a reaction, the total quantity of matter remains unchanged. Understanding this concept is essential for calculating reactants and products in chemical reactions and predicting the outcomes of these processes.