Why is matter neither created nor destroyed during an ordinary chemical reaction?

In an ordinary chemical reaction, matter is neither created nor destroyed because the process involves only the rearrangement of existing atoms rather than their creation or transformation into different elements. This principle is known as the conservation of mass, a foundational concept in chemistry popularized by Antoine Lavoisier.123

Because the total number of atoms of each element remains constant throughout the reaction, the total mass of the reactants must equal the total mass of the products. Consequently, chemical equations must be balanced to reflect this equality, ensuring that the same number of atoms of each kind appears on both sides of the reaction. This understanding, which was central to John Dalton’s atomic theory, confirms that while substances change their chemical identity, the fundamental building blocks of matter are conserved.24