The Law of Conservation of Mass says that in a closed system, the total weight of what you start with (the reactants) will always equal the total weight of what you end up with (the products) after a chemical reaction. This idea was created by Antoine Lavoisier a long time ago, in the late 1700s. It applies to many chemical reactions we see every day.

1. Chemical Reactions in Daily Life:

   • Cooking: When you bake a cake, the weight of all the ingredients you use (like flour, sugar, and eggs) will equal the weight of the cake you make. For example, if you use 500 grams of ingredients, you'll get a cake that weighs around 500 grams, as long as nothing spills or gets thrown away.
   • Burning Wood: When you burn wood, the weight of the wood and the oxygen used will equal the weight of the ash and gases that come out. If you burn 2 kg of wood, the weight of the ash and carbon dioxide that is produced will also be about 2 kg (if you consider moisture and anything else that might be lost).

2. Counting Stuff:

   • For something like burning methane (a type of gas), we can see the balance: $CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O$
   • Here, 16 grams of methane and 64 grams of oxygen come together to make 44 grams of carbon dioxide and 36 grams of water. Before the reaction, everything weighs 80 grams, and after, it still weighs 80 grams.

3. Why This Matters:

   • In science labs, getting accurate weights of the ingredients helps scientists predict what will happen. For example, when doing titration experiments, the weight of what you use should match the weight of what you create. This helps chemists understand concentrations and how much they make.

In short, the Law of Conservation of Mass is all about how matter cannot be created or destroyed during chemical reactions. It shows why it’s important to measure things carefully, both at home and in science experiments.