Bunsen Burner

Description

Burners and flame properties are demonstrated.

Go to Top

Flames and hot objects can cause fires and burns.

Go to Top

Remove flammable and combustible materials from vicinity of flame. Keep a fire extinguisher nearby. Use your finger to determine whether heat is coming from an object that has been heated by the burner. Wait until such an object has cooled before touching.

Go to Top

1. Connect a Bunsen burner to a gas outlet. With some burners and some gas supplies, adjustment of the air vents may be critical. Close the air supply in these cases. Strike a match. Turn on the gas. Bring the lighted match alongside the barrel of the burner and raise toward the top until the gas ignites. Blow out the match. Note the appearance and sound of the flame.
2. Cover the air holes in the burner base with your fingers. Note the appearance and sound of the resulting flame.
3. The color of a hot wire reflects the temperature of the wire. Use the following chart to map the temperature of the flame in °C.

   no light	< 500 °C
   not quite red	500-550 °C
   dark red	650-750 °C
   bright red	850-950 °C
   yellowish red	1050-1150 °C
   not quite white	1250-1350 °C
   white	> 1450 °C

4. Sketch:

   

5. Place a 10-cm length of nichrome (or other wire that will not melt) into a cork holder. Use this wire to probe the regions of the flame. Note the color of the wire after it has heated for a few seconds at the place in the flame being studied. Sketch the flame and indicate temperature at each point.
6. Cover the holes in the base of a burner with your fingers. Hold a flask or beaker containing water in this flame for about 2 minutes. Note the appearance of the glassware. After a suitable cooling period, rub your finger though the dark material on the glassware, and note the appearance of the material on your finger.
7. Place a wire gauze over a lighted burner flame. Observe whether the flame burns above or below the gauze. Observe for 2 minutes.
8. Turn off the burner. Turn on the gas flow. Ignite a match. Hold the gauze above the burner barrel, and light the gas above the gauze. Observe the flame for 2 minutes.
9. Place a fire extinguisher nearby. Have a damp towel available to smother any burning paper. Ignite a burner, and adjust the flame to a large, hot flame. Use tongs to hold a piece of very thick, dense cardboard in the flame so that the plane of the cardboard includes an axis that is perpendicular to the laboratory bench and goes through the center of the burner barrel. Remove before ignition; cool. Note the scorch pattern.
10. Turn off the burner. Push a straight pin through a match below but near the head of the match. Insert the match in a burner barrel so that the head is centered above the barrel. Use the pin as a support for the match. Ignite a different match. Turn on the gas supply. Bring the lighted match to the burner, and ignite the gas. Blow out the lighted match. Observe the match head suspended in the burner barrel. After about 2 minutes, use a cork or other insulator to push the pin so that the match head in the burner barrel enters the bottom of the outer cone of the burner flame. Note what happens, and record.
11. Observe the different types of burners in the burner collection.

Go to Top

Name ___________________________ Class ________

Teacher__________________________

DoChem 007 Bunsen Burner

The gas consists of a solution containing many combustible components. The composition of the mixture is purposefully altered so that, during winter months, the gas has a higher heating value than during the summer. The primary component is always methane, CH₄.

The chemical reaction involved is:

CH₄ + 2O₂ --> CO₂ + 2H₂O

Answer these questions after watching the movie.

1. Describe the sound of the bunsen burner when it is burning with a blue flame.
2. Describe sound, color, and size of the flame when the air to the bunsen burner is reduced.
3. Sketch the bunsen burner flame and indicate the temperature in each region of the flame. Use the color of the wire in the movie to determine the temperature.
4. What is the source of the elemental carbon found on the glassware?
5. Describe the flame when a wire gauze is placed over the flame.
6. Describe the flame when the burner light from above the wire gauze.
7. Sketch the pattern, which was left by the flame, on the card.

Go to Top

Purpose

To demonstrate the characteristics of a Bunsen burner flame.

Go to Top

• Bunsen burner with tubing
• gas supply
• borosilicate glass flask or beaker with water
• matches or spark igniter
• straight pin
• 10 cm nichrome wire inserted into cork
• collection of different types and styles of gas burner
• ring, support stand, tongs
• wire gauze
• 10 cm x 10 cm square of solid, dense cardboard

Go to Top

Students nearly always need instruction on the use of burners.

Go to Top

Teacher set-up: 5 minutes

Presentation: 15-25 minutes

Go to Top

Flames and hot objects can cause fires and burns.

Go to Top

The blackened glassware may be scrubbed with a brush and detergent at a sink. The equipment is reusable. Discard used matches and scorched cardboard, if any, with ordinary solid waste.

Go to Top

Presentation Question:

• What is the source of the elemental carbon found on the glassware?
  • The carbon comes from the natural gas. Many students have never thought about where the carbon comes from, and some believe it comes from the air.

Go to Top

• Most schools have supplies of natural gas. The gas consists of a solution containing many combustible components. The composition of the mixture is purposefully altered so that, during winter months, the gas has a higher heating value than during the summer. The primary component is always methane, CH₄.
• The chemical reaction involved is: CH₄ + 2O₂ --> CO₂ + 2H₂O
• When the flame is adjusted for a bluish-colored two-cone structure, it is noisy. This noisy, blue flame provides the highest possible temperature from the burner. To achieve this, air comes from the region around the barrel, and also is mixed with the gas at the base of the burner.
• By closing the holes at the base of the burner, all of the oxygen used for burning comes from the space near the top of the barrel. The temperature is lower. A quiet flame is formed. Combustion is not complete; elemental carbon, called lamp black, is produced. This is also called soot. The particles of carbon are heated in the flame to give a yellow color. Much more visible light is given off from this flame that a hot, blue flame. The yellow flame is called a luminous flame. This kind of flame was once a main source of street lighting in the United States.
• Flames have structure. The inner cone of a two-coned blue flame does not reach a temperature high enough to impart color to a wire. It is not hot enough to ignite a match head.
• Any condensed phase (solid or liquid) gives off radiation characteristic of its temperature. A range of frequencies of radiation, rather than a single frequency, is emitted. Humans give off radiation characteristic of about 310 K. This radiation is invisible; it appears in the infrared region of the spectrum.
• When sufficiently heated, objects begin to emit visible radiation. The first color to appear is dull red, then red, then orange, and so forth, until the object emits radiation at all visible frequencies and appears white. The temperature of any object may be determined by examining the frequencies of the radiation it emits. On this basis, the apparent temperature of the surface of the sun is about 6000 K. The nichrome wire experiment takes advantage of this effect. The yellow color of the luminous flame is due to this effect.

Go to Top

1. The flame makes a loud hissing or roaring sound.
2. The flame makes less noise. The flame turns yellow and increases in size.
3. The movie colors are not as easy to pick out or as true as the actual experiment, but students can clearly see and inner cone <500 °C and an outer cone that is yellowish or not quite white (1050-1350°C.)
4. The gas is not completely burned to CO₂. Incomplete combustion of the gas leaves carbon behind.
5. The flame remains below the wire gauze as the wire heats and turns red.
6. The flame burns only on top of the wire gauze.
7. The sketch is an oval outline without a bottom.

Go to Top

• Bunsen burner
• Bunsen
• burner
• gas
• natural gas
• combustion flame
• temperature
• flame temperature
• radiation
• visible radiation
• flame cone
• cone
• two-cone

Go to Top