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Combustions
The combustion of carbon
1) Description of the combustion of carbon
Carbon is a substance existing under various forms but the one that may most easily burn is the charcoal (also used in drawing).
- Step 1: initiating combustion.
The initiation allows the combustion to start.
The charcoal is placed in a flame until it becomes hot enough to emit a red light: the charcoal is then incandescent.
- Step 2: Combustion of charcoal in the air
The charcoal is removed from the flame.
Charcoal still burns in the air and remains incandescent.
- Step 3: Combustion of charcoal in the pure dioxygen.
The incandescent charcoal is placed in a container initially containing pure dioxygen.
When the incandescent fusain is placed in the container, a flame forms and some sparks are projected.
Combustion is more intense in pure dioxygen than in air.
- Step 4: End of combustion
After a few moment the combustion becomes less and less intense and then stops.
A part of the fusain has disappeared during combustion.
- Step 5: Analysis of the content of the container where furcoal has burnt.
The limewater test is positive and indicates the presence of carbon dioxide
2) Interpretation of the combustion of carbon
- Combustion is stronger in pure dioxygen (100% dioxygen) than in air (21% dioxygen):dioxygen is required for combustion of charcoal.
- In pure dioxygen combustion stops even if charcoal hasn't totally disappeared. It means that another compound lacks: dioxygen.
Combustion of charcoal consumes dioxygen.
- A part of charcoal (composed of carbon) has disappeared during combustion:
This combustion consumes carbon
-Limewater test indicates the presence of carbon dioxide( limewater turns cloudy): Carbon dioxide has formed during this combustion
- Conclusion:
The combustion of charcoal in dioxygen is a chemical transformation during which some compounds disappear (carbon and dioxygen) and another compound appears (carbon dioxide).
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