Bunsen Burner Soot

This demonstration shows how a Bunsen burner flame changes with oxygen supply. With the air hole closed, the yellow flame results in incomplete combustion, producing soot that can be collected on a cool object. Opening the air hole provides more oxygen, producing a blue flame from complete combustion.

1. Place a Bunsen burner on a heat-proof mat and connect it to the gas supply.
2. Close the air hole on the burner to restrict oxygen flow.
3. Light the burner with a match or striker, producing a yellow safety flame.
4. Hold a wire gauze or clean glass slide just above the flame.
5. Observe soot (black carbon deposits) forming on the surface.
6. Open the air hole to allow more oxygen in and note how the flame turns blue and stops producing soot.

COMPARING BUNSEN BURNER FLAMES - which flame is hottest / cleanest / loudest etc… - Mr Smith's Physics online:

• Try holding different cool surfaces (metal spatula, porcelain, glass) to compare soot collection.
• Compare the heating power of the yellow flame versus the blue flame.
• Use the soot-covered surface to illustrate how incomplete combustion contributes to air pollution.

• Wear safety glasses and tie back long hair.
• Use a heat-proof mat under the Bunsen burner.
• Do not touch hot equipment or surfaces directly after exposure to the flame.
• Ensure proper ventilation, as incomplete combustion may release carbon monoxide.
• Always turn off the gas supply after use.

• Why does the flame produce soot when the air hole is closed? (Because incomplete combustion occurs due to insufficient oxygen, leaving unburned carbon.)
• What changes when the air hole is opened? (More oxygen enters, leading to complete combustion with a blue, hotter flame.)
• How does soot formation relate to real-world pollution? (Soot particles from incomplete combustion contribute to air pollution and health issues.)
• Why is the blue flame preferred for heating in laboratory experiments? (It is hotter, steadier, and does not produce soot.)