The illustration is a camper boiling water in a billy over a camp fire.
a) What physical change in the wood has taken place during preparation of the camp fire?
b) What other physical change is shown taking place?
c) What chemical change is shown taking place?
d) List two ways in which the chemical reaction taking place has been sped up.
The wood had to be chopped or broken to size, which is a physical change. Lighting the wood created a combustion reaction, which is causing a chemical change, converting the wood into carbon dioxide, water, and ash. Boiling the water is another example of a physical change, because the water is simply changing states from liquid to gas.
The chemical reaction of reducing the wood back into CO2 and ash is being done quickly by combustion, rather than slowly by decomposition, which would happen if the wood lay on the ground long enough. The combustion reaction occurred because someone provided ignition by lighting the fire. The fact that the wood was cut or broken into smaller pieces speeds up the reaction, because the smaller pieces expose more surface area so the wood burns faster.