Hint: As it involves a chemical change, burning paper is called a combustion reaction. That's because when we burn a piece of paper, it experiences the combustion reaction, which causes the material's state to transition from solid to liquid to gaseous.
There are three pieces of paper. The first piece is a stretched sheet of paper. The second piece is a crumpled piece of paper, and the third is a wet piece.
The pieces are burnt one by one. We will now observe the changes we see in the papers while burning and the amount of time each paper requires to burn.
Stretched paper: As this piece is stretched, the paper area in contact with the air is more. So burning will take place quickly. The complete piece of paper will turn into ash.
Crumpled paper: This piece is crumbled, so it has developed folds on it. Also, the paper area in contact with air is less, so the burning will take place slowly. However, there will be more soot while burning, and some ash will be produced. The paper will not burn completely. Some parts will be left unburned.
Wet paper: This piece is wetted by water, and we know that water does not burn. The wet paper will burn very, very slowly, and a little smoke will be observed.
The burning of paper, which is a new product, produces ash. Because paper is an organic substance derived from trees, air reacts with hydrogen and carbon, converting some of it to water and carbon dioxide. And this energy is discharged as heat into the environment.