Question

Why does burning wood leaves an ash that is only a small fraction of the mass of the original wood.?

Answer 1

When wood burns, some of the mass is released as a gas. So if you were to combine the small fraction of ash with the gases released, you would get the mass of the original wood.

Answer 2

Step-by-step explanation:

Burning wood leaves an ash which is a small amount of original mass of wood because when we burn wood, large amount of wood is converted into carbon dioxide and water vapor. In complete combustion, there would be no ash remaining, because all the fuel have been consumed completely. When we sum up the mass of gasses released in burning and the ashes we get the original mass.