Chemistry · Interactive
Combustion Reaction
When methane burns it reacts with oxygen to make carbon dioxide and water: CH₄ + 2O₂ → CO₂ + 2H₂O. Drag the slider below to watch the bonds break and re-form while every atom is conserved. Free to use, and exportable into your slides.
Drag the slider to watch methane burn into CO₂ and water. Open fullscreen ↗
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What is a combustion reaction?
A combustion reaction is a reaction in which a fuel reacts rapidly with oxygen and releases energy as heat and light. When the fuel is a hydrocarbon and there is plenty of oxygen, complete combustion produces just two products: carbon dioxide and water. Methane, the main component of natural gas, is the simplest example. Drag the slider in the animation above to watch its bonds break and re-form.
The methane combustion equation
The balanced equation for burning methane is CH₄ + 2O₂ → CO₂ + 2H₂O. One methane molecule reacts with two oxygen molecules to give one carbon dioxide molecule and two water molecules. The coefficients 1, 2, 1, 2 are what make the equation balanced, so the same number of each kind of atom appears on both sides.
Conservation of atoms
Atoms are never created or destroyed in a chemical reaction, only rearranged. On the reactant side there is 1 carbon, 4 hydrogen, and 4 oxygen; on the product side there is also 1 carbon (in CO₂), 4 hydrogen (in the two water molecules), and 4 oxygen (two in CO₂ and one in each water). The animation moves the exact same atoms from reactants to products so you can see mass conservation directly.
Why combustion releases energy
Breaking the bonds in methane and oxygen takes in energy, but forming the strong bonds in carbon dioxide and water releases even more. The net result is that energy is given out, which is why combustion is exothermic and feels hot. Complete combustion with enough oxygen gives a clean flame and only CO₂ and water; limited oxygen leads to incomplete combustion, producing carbon monoxide or soot.
Frequently asked questions
What is a combustion reaction?
A combustion reaction is a rapid reaction between a fuel and oxygen that releases heat and light. Complete combustion of a hydrocarbon produces carbon dioxide and water.
What is the equation for the combustion of methane?
The balanced equation is CH₄ + 2O₂ → CO₂ + 2H₂O. One methane molecule and two oxygen molecules react to form one carbon dioxide molecule and two water molecules.
Is combustion exothermic or endothermic?
Combustion is exothermic. Forming the bonds in carbon dioxide and water releases more energy than is needed to break the bonds in the fuel and oxygen, so energy is given out as heat and light.
How is the methane combustion equation balanced?
With coefficients 1, 2, 1, 2: CH₄ + 2O₂ → CO₂ + 2H₂O. This gives 1 carbon, 4 hydrogen, and 4 oxygen on each side, so atoms are conserved.
What is the difference between complete and incomplete combustion?
Complete combustion happens with plenty of oxygen and yields only carbon dioxide and water. Incomplete combustion happens with limited oxygen and can produce carbon monoxide or soot (carbon) as well.
How do I use this combustion animation?
Drag the reaction-progress slider. The methane and oxygen bonds break and re-form into carbon dioxide and water, and the panel shows the balanced equation and atom conservation. You can also export the animation.