What is conservation of mass in relation to chemical changes?

Conservation of mass in chemical changes refers to the principle that mass cannot be created or destroyed in a chemical reaction.

In more detail, the law of conservation of mass is a fundamental principle in chemistry. It states that in any closed system, the total mass of the reactants (the substances that start a reaction) is always equal to the total mass of the products (the substances that are produced by the reaction). This means that no matter how substances within a closed system interact with each other, the total mass of the system will always remain the same.

This principle is crucial in understanding chemical reactions. For example, if you were to burn a piece of wood, the mass of the wood before it is burnt would be equal to the mass of the ash, smoke and gases produced. Even though it may seem like mass has been lost because the wood has turned into ash and smoke, if you were to collect all the smoke and gases, you would find that their combined mass with the ash is equal to the original mass of the wood.

In chemical equations, this principle is reflected in the fact that the number of atoms of each element in the reactants must be equal to the number of atoms of that element in the products. This is why chemical equations must be balanced. For example, in the reaction between hydrogen and oxygen to form water (2H2 + O2 → 2H2O), there are four hydrogen atoms and two oxygen atoms on both sides of the equation, demonstrating the conservation of mass.

Understanding the conservation of mass is fundamental to studying chemistry, as it underpins how we analyse and predict the outcomes of chemical reactions.