PURPOSE: This exercise has been designed to familiarize students with the use and construction of the Bunsen burner.
INTRODUCTION: The Bunsen burner is an instrument used in science laboratories to provide a convenient and efficient source of heat. Used properly, it can produce temperatures in the 400-500oC range. The fuel is natural gas which is mainly composed of methane. To burn properly, an adequate supply of oxygen is obtained from the surrounding air. This apparatus is constructed to insure a good mixture of methane gas and air to produce a clean hot almost INVISIBLE FLAME.
PARTS AND THEIR FUNCTION: Refer to the accompanying diagram to better understand the various components of the Bunsen burner.
Note: The diagram depicts the exposed cross section of the Bunsen burner as though it had been cut down the middle.
The dotted lines represent the flow of gas through the burner.
The BASE (1) supports the Bunsen burner holding it in an upright position.
Natural gas is provided by the Union Gas Company in pressurized gas pipelines. When the gas valve is opened, gas rushes into the GAS HOSE (2) through a small ORIFICE (hole) (3). The gas moves through the orifice in a very fast moving stream (A) (ex: air escaping from a balloon). As methane gas rushes up into the BARREL (5), it passes openings which permit air to enter the Bunsen burner: AIR VENTS (4). This air is drawn in by the fast moving jet of methane gas (B).
The air and gas then mix together (C) in the barrel which insures a "good mixture" for burning. The mixture of gas and air leave the barrel at the top (D). There is very little heat at this point. IGNITION occurs above the barrel of the burner (E). Light theburner here! If properly adjusted the, flame of the burner will have an INNER CONE (F) and an OUTER CONE (H). The hottest part of the flame is at the tip of the inner cone (G).
** Now carefully review and label the diagram of the Bunsen burner.
SPECIAL FEATURES
AIR INTAKE VALVE: Two types of openings exist depending on the burner you are using. In one design the barrel is threaded into the base and turning the barrel regulates the air openings. Threading up opens while threading down closes.
The other design involves oblong holes with a partial covering sleeve. Rotating the sleeve regulates the opening for air.
GAS NEEDLE VALVE:
This feature permits accurate control of the gas flow into the Bunsen burner.
This valve is usually located at the base immediately under the barrel
at a point below the intake hose: Threading the valve upwards decreases
flow while threading downward increases flow. CAUTION:
This valve can fall out of the Bunsen burner assembly!
TO LIGHT A BUNSEN BURNER:
1. MAKE SURE THE NEEDLE
VALVE AT THE BOTTOM OF THE BURNER IS COMPLETELY SHUTMAKE SURE THE AIR
2. VENTS ARE COMPLETELY SHUT
3. HAVE YOUR MATCHES READY TO LIGHT THE BURNER
4. CONNECT THE GAS HOSE TO THE GAS TAP SECURELY
5. TURN THE GAS TAP VALVE SO THE HANDLE IS PERPENDICULAR TO THE LAB BENCH (POINTS OUT)
6. LIGHT THE MATCH AND HOLD IT OVER THE TOP OF THE BUNSEN BURNER BARREL
7. KEEPING THE BURNER ON THE BENCH, IMMEDIATELY OPEN THE NEEDLE VALVE AT THE BOTTOM OF THE BURNER UNTIL THE BURNER IGNITES.
8. OPEN THE AIR VENTS UNTIL A CLEAR BLUE, QUIET FLAME IS ACHIEVED. A NOISY BURNER FLAME IS DANGEROUS. THIS IS CAUSED BY TOO MUCH AIR. CLOSE THE AIR VENTS UNTIL THE FLAME IS QUIET.
9. ADJUST THE NEEDLE VALVE AND AIR VENTS TO OBTAIN THE FLAME DESIRED.
10. TURN THE GAS OFF AT THE TAP AS SOON AS YOU ARE FINISHED USING THE BURNER.
11. TURN THE GAS OFF AT THE TAP IMMEDIATELY IF ANY PROBLEM OCCURS.
SAFETY SAFETY SAFETY
ALWAYS KEEP A SAFE DISTANCE FROM A BUNSEN BURNER. TUCK IN OR TIE BACK LOOSE CLOTHING AND LONGHAIR. ANY BURN SHOULD BE WASHED IN COLD WATER IMMEDIATELY FOR AT LEAST10 MINUTES. NOTIFY YOUR TEACHER IF ANY ACCIDENTS OCCUR.
SAFETY PRECAUTIONS:
THE FLAME IS ALMOST INVISIBLE AND AS A RESULT THERE WILL BE A HIGH RISK OF GETTING PAINFUL BURNS IF PRECAUTIONS ARE NOT TAKEN.
You must KNOW the following safety precautions:
1. NEVER turn on the gas until you are completely ready to light the burner. Have the match lit before you turn on the gas.
2. ALWAYS keep a safe distance from the burner whether lit or not
3. NEVER leave a lit burner unattended. Turn it off as soon as you are finished!
4. Keep notebooks and other flammables away from the flame. The bench area where you are working should not be cluttered.
5. NEVER reach over a burner.
6. Keep the flame to a minimum at all times. (Teacher Guidelines)
7. Treat a burn with running cold water immediately for several minutes until the burning sensation stops.
8. Only heat up what the lab procedure indicates.