Bunsen Burner Flame Experiment Notes

Materials

  • Bunsen burner

  • Heatproof mat

  • Matches

  • Safety glasses

  • Paper clip

  • Tongs

  • Pin

Safety Precautions

  • Wear safety glasses.

  • Ensure the Bunsen burner is on a heatproof mat.

  • Tie back long hair.

Method

Part A

  1. Hang an unburnt match over the barrel of a Bunsen burner using a pin.

  2. Light the Bunsen burner according to instructions.

  3. Open the air hole to produce a blue flame.

  4. Turn off the Bunsen burner.

  5. Remove the match and pin with tongs.

  6. Record observations of the match's appearance.

Part B

  1. Re-light the Bunsen burner and adjust the air hole to produce a blue flame.

  2. Use tongs to hold the wire across the flame, close to the barrel of the Bunsen burner.

  3. Note the changes to the wire.

  4. Move the wire up slightly and record observations.

Results

  • Observations for Part A (match appearance).

  • Observations for Part B (wire changes).

Discussion Questions

  1. What happens to the match hanging over the barrel? Explain why.

    • The match does not ignite when hanging over the barrel before the flame is lit.

    • This is because unlit gas is escaping from the burner, but there is no heat or flame to cause ignition.

    • Once the Bunsen burner is lit, the match may show signs of slight scorching or charring, indicating some heat exposure from rising warm air and gas.

  2. What color does the wire become when held across the flame?

    • When held in the blue flame near the barrel, the wire becomes red or orange, indicating it is being strongly heated.

  3. Is the color of the wire different when it is held at the top of the flame?

    • Yes. When the wire is held at the top of the flame, it becomes less brightly colored— often a dull red—because this area is cooler than the tip of the inner cone.

  4. Draw a diagram of the Bunsen burner flame, labeling the hottest parts.

    • Outer cone: Light blue, less hot

    • Inner cone: Dark blue

    • Tip of inner cone: Hottest part of the flame — this is where the wire or object should be placed for maximum heating.

  5. Why would it be unwise to position the test tube at the base of a blue flame when heating substances in a test tube with a Bunsen burner?

    • It would be unwise because the base of the flame is not the hottest part.

    • Heating a test tube there results in inefficient heating and may cause uneven expansion, risking cracking or spillage.

    • Also, this area may allow unburnt gas to accumulate.

  6. Why is the yellow flame often called the safety flame?

    • The yellow flame is called the safety flame because it is easily visible, indicating that the air hole is closed and combustion is incomplete, resulting in a cooler, more stable flame that is less likely to cause burns or accidents.

Conclusion

The hottest part of a blue flame is at the tip of the inner blue cone, where objects should be placed for effective heating.