Atomic Foundations of Matter | Class 9 Science Notes

Law of Conservation of Mass

The Law of Conservation of Mass is a fundamental principle in chemistry which states that mass can neither be created nor destroyed in a chemical reaction. This law was proposed by Antoine Lavoisier in 1789 and is based on careful experimental observations. The law implies that the total mass of the reactants before a chemical reaction is equal to the total mass of the products after the reaction. This principle is demonstrated through experiments such as mixing baking soda and vinegar in a closed system, where the total mass remains constant despite the formation of new substances and the release of gases. The law applies universally to all chemical reactions and helps in understanding the quantitative aspects of chemical changes. It also forms the basis for balancing chemical equations and stoichiometric calculations. The law was a significant advancement in chemistry, dispelling earlier misconceptions about matter disappearing or being created during reactions.

📊 Diagram: Fig. 9.2: (a) Weight of vinegar and baking soda; Fig. 9.2: (b) Pouring baking soda into the conical flask containing vinegar; Fig. 9.3: (a) Weight of vinegar and baking soda; Fig. 9.3: (b) Pouring baking soda into the conical flask containing vinegar; Fig. 9.3: (c) Weight of the final reaction mixture; Antoine Lavoisier is known as the Father of Modern Chemistry. He proposed the Law of Conservation of Mass. This law applies to every chemical reaction. Lavoisier continued to study this and proposed t; Fig. 9.4: (a) Weight of solutions (reactants) before mixing; Fig. 9.4: (b) Weight of products after mixing

🧪 Activity: Activity 9.2: Investigate the Law of Conservation of Mass by reacting baking soda and vinegar in two experimental setups, one open and one closed, to observe mass changes.

🔗 Connection: This section leads to the Law of Constant Proportions, which explains the fixed ratios in which elements combine to form compounds.