EVERYDAY SCIENCE

Detailed explanation-1: -When wood is set on fire, the Carbon present in the form of Methane or butane combusts in the presence of Oxygen to form water and Carbon dioxide. The burning of wood is a chemical change as it leads to the formation of new substances like Carbon dioxide gas, water vapour, ash, etc.

Detailed explanation-2: -The burning of wood leads to the formation of new substances like ash(carbon), carbon dioxide gas, water vapour, heat and light. This change is irreversible and hence a chemical change. While cutting wood into smaller pieces is a physical change as there is no change in the original composition of wood.

Detailed explanation-3: -Ignition and combustion of wood is mainly based on the pyrolysis (i.e. thermal decomposition) of cellulose and the reactions of pyrolysis products with each other and with gases in the air, mainly oxygen. When temperature increases, cellulose starts to pyrolyse.

Detailed explanation-4: -Burning is an example of a chemical change. Signs of chemical change include the release of bubbles, a change of color, production of an odor, release of heat and light, and production of loud sounds.

Detailed explanation-5: -Cutting of wood into small pieces is a irreversible physical change as no new substance is formed and there is no change in chemical composition of wood. Whereas, burning of wood is a chemical change as a new substance is formed.