When CH₄ burns with the presence of O₂, CO₂ and H₂O are formed as the products. The balanced equation is;
CH₄ + 2O₂ → CO₂ + 2H₂O
When the reaction happens, 4 C-H bonds of CH₄ and O=O bond of O₂ are broken down to form 2 C=O bonds in CO₂ and 2 O-H bonds in H₂O.
The broken and formed bonds are marked in the image.