Balancing a chemical equation is an important skill in chemistry, especially for Year 8 students. It helps us see that matter stays the same during a reaction. This means the same number of atoms must be on both sides of the reaction. Let’s go through the simple steps to balance a chemical reaction!

Understanding the Law of Conservation of Mass

Before we start balancing, it’s important to understand the law of conservation of mass. This law says that matter cannot be created or destroyed in a chemical reaction. So, the total number of atoms for each element must be the same on both sides of the equation.

Steps to Balance a Chemical Reaction

1. Write the Unbalanced Equation
   Start with the unbalanced chemical equation. Let’s look at the combustion of propane:

   $\text{C}_3\text{H}_8 + \text{O}_2 \rightarrow \text{CO}_2 + \text{H}_2\text{O}$

2. Count the Atoms
   Next, count the atoms of each element on both sides of the equation. Here’s what we have for propane:

   • Reactants:
     • Carbon (C): 3
     • Hydrogen (H): 8
     • Oxygen (O): 2
   • Products:
     • Carbon (C): 1 (in CO₂)
     • Hydrogen (H): 2 (in H₂O)
     • Oxygen (O): 3 (2 from CO₂ and 1 from H₂O)

3. Start Balancing with Single Elements
   Now, let’s balance the elements that appear in only one reactant and one product first. We’ll start with carbon (C).

   To balance carbon, we need to put a 3 in front of CO₂:

   $\text{C}_3\text{H}_8 + \text{O}_2 \rightarrow 3\text{CO}_2 + \text{H}_2\text{O}$

4. Balance the Hydrogen Atoms
   Next, we’ll balance the hydrogen (H) atoms. To do this, we need 4 water molecules because we have 8 H atoms in the propane:

   $\text{C}_3\text{H}_8 + \text{O}_2 \rightarrow 3\text{CO}_2 + 4\text{H}_2\text{O}$

5. Balance the Oxygen Atoms
   Finally, we need to balance the oxygen (O) atoms. On the product side, we have:

   • From 3 CO₂: $3 \times 2 = 6$ O
   • From 4 H₂O: $4 \times 1 = 4$ O

   Adding these gives us a total of $6 + 4 = 10$ O on the product side. In the reactants, the oxygen only comes from O₂, which has 2 O atoms in each molecule. We need 10 O atoms from O₂, so we need 5 O₂ molecules:

   $\text{C}_3\text{H}_8 + 5\text{O}_2 \rightarrow 3\text{CO}_2 + 4\text{H}_2\text{O}$

Final Check

Let’s do a quick check to make sure everything is balanced:

• Reactants:

  • C: 3
  • H: 8
  • O: 10 ($5 \times 2$)

• Products:

  • C: 3 (from 3 CO₂)
  • H: 8 (from 4 H₂O)
  • O: 10 (6 from 3 CO₂ + 4 from 4 H₂O)

Both sides have the same number of each type of atom, so our equation is balanced!

Conclusion

Balancing chemical equations can be a fun puzzle. By following these steps, you can keep the balance that the law of conservation of mass requires. Practice with different reactions, and soon balancing equations will be easy for you!