Using carbon fuels
The Bunsen burner is commonly used in school laboratories to heat chemicals. Its fuel is natural gas, which is almost pure methane, CH4. Methane is a hydrocarbon. So the Bunsen burner has an air hole that allows complete or incomplete combustion.
When the air hole is open, air is drawn into the chimney, where it mixes with the natural gas. This ensures complete combustion:
methane + oxygen → carbon dioxide + water
A very hot, blue flame is produced.
When the air hole is closed the natural gas can only mix with air at the mouth of the chimney. Incomplete combustion occurs as a result:
methane + oxygen → carbon monoxide + carbon + water
A yellow flame is produced, which transfers less heat energy than the blue flame. The yellow flame is brighter than the blue flame because the specks of carbon glow when heated.
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