Why does burning wood produce ash?

Question

Why not just a block of coal instead of powder?

In: 0

Answer 1

Wood is made mostly of hydrocarbons. Long chains of hydrogen and carbon, with some nitrogen and oxygen on there too. Then there’s water. These all become a gas during the burning of the wood.

Then there are the minerals. Not much of the wood’s weight is minerals, but they’re important to the tree. As the tree burns, the minerals generally do not become a gas. For instance, the potassium forms potassium oxide. The phosphorous, phosphorous pentoxide. These form your ash.

So the order goes:

Wood burns by releasing the non-carbon part of hydrocarbons. This makes a billowing flame.

The leftover carbon, the coals, burn at their surface. They do not create a billowing flame but instead glow.

Finally, as the coals slowly vanish, you’re left with ash.