When wood burns, it undergoes a series of physical and chemical changes. Here’s a breakdown of the process:
-
Heating and Drying: Initially, as the wood is exposed to heat, any moisture contained within it evaporates. This is why dry wood burns more efficiently than wet wood.
-
Pyrolysis: As the temperature rises, the wood begins to break down in a process known as pyrolysis. This involves the thermal decomposition of the chemical components of the wood, primarily cellulose, hemicellulose, and lignin. During pyrolysis, volatile gases, tar, and charcoal are produced.
-
Flaming Combustion: Once the temperature is sufficiently high, the volatile gases released during pyrolysis ignite, producing visible flames. This stage is characterized by a rapid release of energy, light, and heat.
-
Charcoal Formation: As the volatile materials continue to burn off, the remaining solid material (carbon-rich charcoal) can continue to burn if there is enough heat and oxygen. This phase represents smoldering combustion, where the wood slowly converts into ash.
-
Ash Formation: Finally, as the combustion process continues, the remaining material is reduced to ash, a mix of inorganic minerals. The ash is typically much lighter and has a different chemical composition compared to the original wood.
Throughout these stages, the wood changes in color, temperature, and physical state, from solid to gas, as it transforms through combustion, ultimately releasing energy in the form of heat and light. The overall process is an example of exothermic reaction, where energy is released.
1 answer