The Law of Conservation of Mass says that in a closed system, mass cannot be created or destroyed when a chemical reaction happens. This idea is very important when we balance chemical equations. It means the mass of the starting materials (reactants) must be the same as the mass of what we end up with (products).

Key Points About Balancing Chemical Equations:

1. Mass Matters:

   • The total mass of the reactants (the stuff before the reaction) has to be equal to the total mass of the products (the stuff after the reaction).

2. Counting Atoms:

   • We need to count the atoms of each element. For example, in the reaction where hydrogen and oxygen form water: $2H_2 + O_2 \rightarrow 2H_2O$
   • Reactants: We have 4 hydrogen atoms and 2 oxygen atoms.
   • Products: We also have 4 hydrogen atoms and 2 oxygen atoms here too.

3. Steps to Balance:

   • Step 1: Write down the equation that is not balanced yet.
   • Step 2: Count how many atoms are in each element.
   • Step 3: Add numbers in front (called coefficients) to balance the atoms.
   • Step 4: Double-check to make sure all the elements are balanced.

Conclusion:

By following the Law of Conservation of Mass, chemists make sure that chemical equations are balanced. This shows that matter stays the same during a reaction.