If you spend time in a chemistry class, you have to learn how to balance equations. Although this may seem like a tedious task, it demonstrates a fundamental law of matter. Making sure both sides of an equation match up on an atomic level demonstrates the law of the conservation of mass.
TL;DR (Too Long; Didn't Read)
Balancing equations demonstrates the fundamental law of the conservation of mass. It shows that you cannot create or destroy mass in a chemical reaction, so the mass stays constant.
Fundamental Law of the Conservation of Mass
The law of the conservation of mass states that the total weight of a reaction cannot change because matter cannot be destroyed or created. During a chemical reaction, the mass of the reactants and products must be the same. The total number of atoms stays equal. Elements cannot magically appear or disappear in a reaction, so you have to account for all of them.
History of the Law of the Conservation of Mass
In 1789, Antoine Lavoisier found that you cannot destroy or create matter, and the law of the conservation of mass was born. Although he gets most of the credit, he was not the first person to discover or notice this fundamental law in nature. During the fifth century, the Greek philosopher Anaxagoras said that you cannot create or destroy anything because everything is a rearrangement of prior ingredients.
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How to Balance Equations
To balance a chemical equation, you make sure the number of atoms for all the elements is the same on both sides – the number of atoms on the reactant side must match the amount on the product side. You cannot change the actual formula while balancing the equation.
Start the process by counting the number of elements on each side. Then, check if both sides are the same. If they are not, use coefficients, which are numbers in front of the formulas, to balance them.
For example, to balance the equation N2 + H2 -> NH3, you would have to make it N2 + 3H2 -> 2NH3, so all the atoms match up on both sides.
A balanced chemical reaction has the same number of atoms on the reactant and product sides. You can use coefficients to achieve this balance, such as multiplying by three and two as in the example.