Why does paper burn?
Paper is mostly cellulose, long sugar chains made by plants. Heat unzips them; oxygen finishes the job, releasing trapped sunlight as fire.
Paper is stored sunlight
Trees and other plants build cellulose by stitching glucose molecules together, and the energy to make those bonds came from the sun. Paper, in a real sense, is light in solid form.
The chain reaction of fire
match heats paper to ≈ 230 °Ccellulose breaks into volatile gasesbecause long chains can’t hold together when shaken hard enough
those gases mix with airthey ignite and glowbecause carbon and hydrogen love oxygen
the flame heats more paperthe reaction sustains itselfbecause fire is its own ignition source until fuel runs out
Why the ash is so light
Most of the paper’s mass leaves as carbon dioxide and water vapour. What remains is the mineral skeleton, calcium, potassium, a touch of iron, flakes that weigh almost nothing.