After a bonfire, ash can be considered evidence of a chemical change. Here's the distinction:
Evidence of a Physical Change:
- Remaining Charcoal or Unburnt Wood: This is an example of a physical change if the charcoal is not consumed; it has merely changed in appearance (e.g., from wood to charred wood), but its chemical composition hasn’t been fundamentally altered.
Evidence of a Chemical Change:
- Ash: The presence of ash indicates that a chemical change has occurred. During the bonfire, the organic materials in the wood (cellulose, lignin, etc.) undergo combustion, resulting in the formation of ash, smoke, gases, and other byproducts. The original materials have transformed into different substances, indicating a permanent change in chemical composition.
In summary, ash signifies a chemical change, while remaining charcoal could represent a physical change, depending on whether it has been completely converted to ash or not.