The Elements in Wood

• An element is a pure chemical substance, meaning that it only has one type of atom in its structure; an atom is simply the building block for an element. Wood contains an element called carbon, which is the most prevalent element in living things, both animal and vegetable. Carbon is found in common products like graphite, used to make pencils.
  
  

Chemical Reaction

• When it burns, the carbon in wood is reacting with oxygen in the atmosphere. Oxygen is another element found in many living things, including the air we breathe. As wood burns, the carbon reacts with the oxygen and produces carbon dioxide. Carbon dioxide comprises one carbon atom and two oxygen atoms.
  
  

Production of Heat

• When compounds like carbon dioxide are formed, they often generate heat as a product of the reaction. A reaction in which heat is produced is called an exothermic reaction; burning wood is an example of an exothermic reaction.
  
  

Smoke and Soot as Byproducts

• After heat is produced and carbon dioxide is given off, there are soot and smoke left as byproducts. A byproduct is a product of a reaction this is not the main goal of initiating that reaction. Smoke forms because non-carbon elements in the wood are reacting with the heat and giving off fumes. Soot forms on the wood when the reaction between carbon and oxygen is incomplete, leaving a black residue.
  
  

When the Wood Has Stopped Burning

• Once the all the carbon in the wood has been consumed, the fire will stop burning; there will be only black ash and burnt coals left. This material will no longer support a reaction that produces heat and carbon dioxide.