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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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