Methane burns in oxygen to form carbon dioxide and water.
Step 1 — Unbalanced: CH₄ + O₂ → CO₂ + H₂O
Step 2 — Count: C: 1=1 ✓ | H: 4 vs 2 ✗ | O: 2 vs 3 ✗
Step 3 — Balance H first (fix H₂O): CH₄ + O₂ → CO₂ + 2H₂O
Step 4 — Recount O: Left: 2 | Right: 2+2=4 ✗ → add 2O₂
Step 5 — Balanced: CH₄ + 2O₂ → CO₂ + 2H₂O ✓
Figure 1: Systematic balancing — work through one element at a time, check all at the end.
Quick Check: Balance this equation: Na + H₂O → NaOH + H₂
2Na + 2H₂O → 2NaOH + H₂ (multiply the Na and NaOH by 2, then check: Na 2=2, H 4=4, O 2=2)
This diagram covers Balancing a Combustion Equation — Worked Example within Formulae, Equations and Conservation of Mass for GCSE Chemistry. Revise Formulae, Equations and Conservation of Mass in Quantitative Chemistry for GCSE Chemistry with 13 exam-style questions and 12 flashcards. This topic shows up very often in GCSE exams, so students should be able to explain it clearly, not just recognise the term. It is section 5 of 14 in this topic. Focus on the labels, the relationships between parts, and the explanation that turns the diagram into an exam-ready answer.
Practice questions for Formulae, Equations and Conservation of Mass
Which of the following is the correct formula for oxygen gas?
Explain why mass is conserved in a chemical reaction.