Name______

THE BUNSEN BURNER AND FLAME LAB

The burner at your bench is an adaptation of the one invented by Robert Bunsen, a celebrated chemist of the last century, whereby fuel gas and air can be mixed and burned advantageously and safely.

  1. The Bunsen Burner: Examine carefully the burner which is at your bench. Take it apart and study each of its parts. Notice particularly the gas inlet and the air inlet and the manner in which the flow can be controlled in each. The type and size of the flame which you get will be due to the mutual adjustment of these two inlets.

1. Where is the air inlet located? ______

2. Where is the gas inlet located? ______

  1. The Bunsen Flame: Light the burner and completely close the air inlet. (Often it is difficult to close the air inlet holes completely. If you do not get a yellow flame, try holding your hand around the openings at the base.
  1. What is the color of the flame which has insufficient air? ______

Now hold the end of a glass tube or glass stirring rod in the yellow flame for a few seconds:

  1. What collects on the glass or porcelain? ______

The gas which we use is largely methane (CH4), a compound of hydrogen and carbon (Some sulfur products are present as impurities and give the gas its disagreeable odor). When the gas burns without a sufficient supply of air or oxygen, the hydrogen, which is much more combustible than the carbon, combines with most of the oxygen. This leaves much of the carbon left uncombined. This carbon is heated to incandescence, which gives the yellow color to the flame, and which makes the flame luminous. an abundance of air mixed with the gas, on the other hand, would burn the carbon and produce a flame without any yellow. Such a flame obviously, is more efficient for ordinary use. Such a flame is often called colorless although it will always have a faint blue color.

  1. Temperature of the Bunsen Flame

The temperature of flames can be determined
roughly by the color imparted to objects held in the
flame. A wire, for instance, becomes incandescent
just as the carbon did above. The approximate
temperatures corresponding to heat color for iron
wire are:
500ºC / faint red
700 ºC / red
1100 ºC / orange
1500 ºC / white
Open the air inlet of the burner to get a “colorless”
flame. Insert the tip of the steel wire into the flame at
several points.
Make a drawing of the Bunsen flame in the space
which is provided, and indicate on the drawing the
approximate temperatures at the points which you select. Return the wire.

5. At what point is the flame the hottest? ______

6. Approximately, what is the highest temperature of the flame? ______

7. Copper melts at 1083ºC. Using your forceps, hold the end of a piece of copper wire in the flame. What are the results?

8. What conclusions would you draw concerning the temperatures of the flame from the copper experiment?

9. Hold a piece of cardboard briefly in the flame below the tip of the inner flame. Examine it. Hold another portion of the cardboard in the flame above the inner flame. If the cardboard should ignite, the flame may be put out by running water on it. It should be obvious that a burning object should not be thrown into the waste basket. When extinguished, the wet cardboard should not be left in the sink but should be put in a waste basket.

State the effect of the flame for each position.

10. In what way does this confirm or dispute your previous observations with reference to the Bunsen flame?

11. Application: Gasoline is a hydrogen and carbon compound. It is mixed with air in the carburetor of a car. What conditions within the carburetor would cause carbon to be deposited in the cylinders of the engine?