1. Chemical Balancing The Law of Conservation of Mass:
No matter can be created or destroyed in a chemical reaction!
So, the number of atoms that are present in the reactants has to balance the number of atoms that are present in the products.

2. How to Balance Chemical Equations
Step One:
Write down worded equation first and then the equation.
Propane + Oxygen Gas  Water + Carbon Dioxide
𝐶3𝐻8 + O2  H2O + CO2

3. How to Balance Chemical Equations
Step Two:
Write down the number of atoms per each element that you haven on each side of the equation. (Tables can make it easier!)
Element
Reactants
Products C 3 1 H 8 2 O 2 3
When balancing the equation, always leave Hydrogen and Oxygen for last.

4. How to Balance Chemical Equations
Step Three:
If you have more than one element to balance, start with the element that appears in only single molecule of reactants and in only a single molecule of products.
So, we start with Carbon atoms first.

5. How to Balance Chemical Equations
Step Four:
Add a coefficient to the single carbon atom on the right of the equation to balance it with the 3 carbon atoms on the left of the equation.
Balanced
𝐶3𝐻8 + O2  H2O + CO2 3
Balanced
Element
Reactants
Products C 3 1
x3 = 3 H 8 2 O 2 3

6. How to Balance Chemical Equations
𝐶3𝐻8 + O2  H2O +3CO2
Step Five:
Balance the Hydrogen atom next. You have 8 on the left side, so you need 8 on the right side. On the right side, add a 4 as the coefficient.
Now there are 10 Oxygen atoms
Balanced
𝐶3𝐻8 + O2  H2O +3CO2 4
Element
Reactants
Products
Balanced C 3 3 H 8 2
x4 = 8 O 2 10 3

7. How to Balance Chemical Equations
𝐶3𝐻8 + O2  4H2O +3CO2
Step Six:
Now balance the oxygen atom. There are 10 molecules in the product side but only 2 in the reactants side. So place a coefficient of 5 in the reactants.
Balanced
𝐶3𝐻8 + O2 4H2O +3CO2 5
Balanced
Element
Reactants
Products C 3 3 H 8 8 O 2
x5 = 10 10

8. How to Balance Chemical Equations
Now your equation is balanced and should look like this:
𝐶3𝐻8 + 5O2 4H2O +3CO2
Element
Reactants
Products C 3 3 H 8 8 O 10 10
Since the Laws of Conservation of Mass has been maintained the equation is complete!