LAB- USING A BUNSEN BURNER
Purpose: To become familiar and comfortable with the operation of the Bunsen
burner. To cut, fire polish, and bend glass tubing.
Equipment: Bunsen burner, flint striker, triangular file, glass stirring rod, and
ceramic fiber pad
Materials: Glass tubing, paper clips, and wooden matches
Introduction:
In the first part of this experiment you will learn how to properly operate a
Bunsen burner. The chemical reaction that occurs in a Bunsen burner is called
combustion. Combustion is an exothermic reaction that produces heat and
sometimes light energy when a fuel is burned in the presence of oxygen gas. The
fuel we use in our lab is propane gas, C3H8. Bunsen burners are made in a
variety of designs. However, in every case there must be some means of igniting
the reaction and regulating the amount of oxygen that enters the burner and
mixes with the fuel. On our Bunsen burners the amount of air or actually, oxygen
gas (O2), is controlled by a set of holes that open and close as the collar of the
burner is turned. A needle valve at the bottom of our burners is used to regulate
the amount the propane gas (C3H8). The reaction is ignited with a flint striker.
Many common devices use combustion as a source of heat. Some
examples include fireplaces, wood stoves, furnaces, grills, gas stoves, gas
dryers, gas hot water heaters, kerosene space heaters, Coleman lanterns,
Coleman stoves, and even automobiles. Combustion may be complete or
incomplete depending on whether or not there is sufficient oxygen gas present to
react with the fuel.
If you see a blue flame you know complete combustion is occurring and an
adequate amount of oxygen gas is present to safely burn the fuel and produce
carbon dioxide and water.
Complete Combustion: Fuel + Oxygen  Carbon dioxide + Water + Energy
This example is for propane fuel: C3H8(g) + 5 O2(g)  3 CO2(g) + 4 H2O(g)
Incomplete combustion occurs when there is not enough oxygen gas
present to completely react with the fuel. Incomplete combustion is extremely
dangerous to plants, animals, and humans. During incomplete combustion a
deadly toxic colorless gas undetectable by smell called carbon monoxide (CO) is
produced instead of carbon dioxide (CO2).
Incomplete combustion can be recognized in several ways. You will know
incomplete combustion is occurring if the flame is much larger than it is supposed
to be and is largely yellow in color. Other signs of incomplete combustion include
plants suddenly dying, soot collecting on surfaces and excessive water vapor
forming on windows and cool surfaces. Soot is a black solid composed of the
element carbon. A secondary reaction resulting from incomplete combustion
produces aldehydes. Aldehydes can be detected by smell and the metallic taste
they leave in your mouth.
Health symptoms of carbon monoxide poisoning include severe headache,
dizziness, nausea, shortness of breath, light-headedness, and mental confusion.
Prolonged exposure can even lead to death. If you suspect you have been
poisoned, immediately seek fresh air and medical attention. A simple blood test
can detect if you have elevated CO levels. The best way to prevent CO poisoning
is to install carbon monoxide detectors throughout your home and keep your
furnace and any other heating devices in good working order.
Special Safety Rules for Heating Substances in the Science Lab:
1. As always wear your safety goggles, apron, and closed toe shoes. Also
be sure to tie back long hair and secure loose or bulky clothing. Make
sure hair, clothing, hands, and any combustible materials are a safe
distance from the flame at all times. Never reach or lean over the flame.
2. Never leave a lit burner unattended. Turn the burner off using the gas jet
when not in use.
3. Do not point the open end of a test tube being heated at yourself or
anyone else. Never heat a test tube while the stopper is still in it. Never
look into a container that is being heated.
4. Heated metals and glass remain very hot for a long time. They should be
set aside to cool using tongs. Never put hot glassware in cold water as
the glassware may break or crack.
5. Do not place hot glassware directly on the lab table. Always put hot
apparatus on a ceramic fiber pad and allow plenty of time for it to cool
before touching it.
6. Determine if a heated object is cool enough to touch by bringing the back
of your hand close to it. If you feel heat, do not grasp the object until
further cooling occurs.
Part 1 – The Bunsen Burner
LIGHTING THE BUNSEN BURNER
A. With your instructor’s help examine the parts of your Bunsen burner and then
complete the following table.
Part of Burner
Function
Barrel
Collar
Needle valve
Base
Barrel
Collar
Base
Propane Gas Inlet
Needle Valve
B. Follow the instructor’s directions to adjust the burner. Generally, the burner
should be adjusted so the needle valve is about ½ of a turn open and the
collar is about ¼ of the way open. Always turn the propane gas on and off
using the gas jet at the lab counter, not the needle valve on the bottom of the
burner. DO NOT LIGHT THE BURNER UNTIL YOU ARE DIRECTED TO DO
SO.
C. We use a flint striker, not matches, to light our burners. Your teacher will
demonstrate the proper technique for using the striker. Always hold the
striker about 2 cm above and just to the side of the top of the barrel. Be sure
your hand is not above the opening of the barrel. When directed by your
teacher, practice making sparks with your striker 2 or 3 times.
D. When directed by your teacher, open the gas jet at the lab counter and use
your striker to light the burner. If your burner does not light after two or three
attempts, immediately turn off the gas jet and consult your teacher for help.
E. Adjust the collar until you have a quiet, steady flame with a sharply defined
inner blue cone. If the collar is opened too far, too much air enters the burner
and a roaring noise is heard. If the collar is not open far enough, too little air
enters the burner and the flame turns yellow in color or goes out.
F. Adjust the needle valve to give a flame extending roughly 8 cm above the
barrel. If the needle valve is opened too much, too much propane gas enters
the burner and the flame is dangerously tall. If the needle valve is not opened
enough, too little propane enters the burner, and the flame is either too short
or goes out.
G. When finished using the burner, always turn the burner off by closing the gas
jet at the lab counter. It is NOT necessary to close the collar and needle
valve.
H. After you have practiced lighting and adjusting your burner at least 10 times,
have your teacher sign the verification box.
Teacher Verification
Initials:
Date:
INCOMPLETE COMBUSTION
I. When given the approval by your instructor, use your striker to re-light the
burner. Slightly close the collar so less air (and oxygen gas) is allowed to
enter the burner. Continue to close the collar until there is a noticeable
change in the color of the flame. Not only is this flame not hot enough to be
useful in the lab but it also produces toxic carbon monoxide gas.
1. What is the color of the flame when the collar is closed and not enough air
is allowed to enter the burner? ____________________________
J. While the collar is still closed, hold one end of your glass-stirring rod in the
flame for about 20 seconds. Then, set the hot end of the glass-stirring rod on
your ceramic fiber pad to cool.
K. Make the necessary adjustments so that the flame is once again about 8 cm
high with a distinct inner blue cone. Turn the burner off by closing the gas jet.
Do not close the collar and needle valve.
2. Based on the flame color, was complete or incomplete combustion
occurring? ______________________________________
3. Name the gas produced that causes this type of combustion to be
dangerous. ______________________________________
4. What is the color of the deposit on the glass-stirring rod? _____________
5. What is the elemental composition of this soot?__________________
6. Why did this deposit form on the glass-stirring rod when the collar of the
Bunsen burner was closed?
__________________________________________________________
__________________________________________________________
_________________________________________________________
LIGHTING A WOODEN MATCH
L. Following your teacher’s example, attach a paper clip to a wooden match so
that the wooden match may be rested in the opening of the barrel of the
Bunsen burner. Then light the burner with your striker. Observe what
happens to your match as well as those of others in your lab.
M. Turn off your burner.
7. Did everyone’s match light immediately? _________
8. In terms of temperature, explain your answer to #5.
_________________________________________________________
_________________________________________________________
_________________________________________________________
9. Sketch a picture of your Bunsen burner flame and label the area of the
flame that is hottest. Be specific. Use of color is encouraged.
10. How can you test to see if your glass stirring-rod has cooled off enough to
handle with your bare fingers?
___________________________________________________________
___________________________________________________________
___________________________________________________________
N. When cool, wipe the deposit off the glass-stirring rod with a wet paper towel
and return it to its proper place.
O. Dispose of the match and paperclip as directed by your teacher.
Part 2 – Manipulating Glass Tubing
The glass tubing used in chemistry labs is typically made of a relatively soft
glass that has a low melting point and can be easily scratched and broken.
However, the ends of freshly cut glass tubing are very sharp and must be
smoothed by fire polishing them before the glass tubing can be safely used.
Since many chemistry experiments require glass tubing that has been bent you
will practice three new skills today: cutting, fire polishing, and bending glass
tubing.
A. CUTTING GLASS TUBING – Carefully examine the diagram on the next
page before attempting this part. Place a 30 cm piece of glass tubing flat on
the lab table. At the point to be cut, make a deep scratch at right angles by
pushing the edge of a triangular file away from you with one firm, steady
stroke. Grasp the tubing with both hands, with your thumbs meeting opposite
the scratch, and break it by pulling the ends toward you. The tubing should
break at the scratch mark.
1. With a single stroke,
scratch the tube with the
edge of a triangular file.
2. Place thumbs together
opposite the scratches,
with the scratch away
from you.
3. Pull and bend quickly
but gently toward
yourself.
11. Explain why you must scratch the glass before using force to break the
glass tubing?
________________________________________________________
________________________________________________________
________________________________________________________
Caution
To avoid serious burns, never touch glass tubing before making
certain that the tubing is cool. Holding the back of your hand
near – but not touching – the tubing will reveal the approximate
temperature of the tubing. Never put the hot tubing in cold water.
B. FIRE POLISHING – The edges of the tubes you have just cut are very sharp.
Fire polish by holding the end of the tube in the burner flame while rolling the
tube gently between the fingers to heat it uniformly. Be sure to hold the tube
in the hottest part of the burner flame. As the flame above the tubing yellows,
the glass softens, and its sharp edges become rounded. Allow the glass to
cool on the ceramic fiber pad and then repeat the procedure until the ends of
both pieces of glass tubing are fire polished.
Fire-polish ends by rotating
end of tube in flame.
Cut end
Correctly fire-polished
Tube has been heated too much
12. When fire polishing, why is it unwise to keep the cut end of the tubing in
the flame for too long of a time?
__________________________________________________________
__________________________________________________________
__________________________________________________________
13. Why is it unwise to use glass tubing that has not been fire-polished?
__________________________________________________________
__________________________________________________________
__________________________________________________________
14. Is glass a good conductor of heat? __________ How do you know?
_________________________________________________________
_________________________________________________________
_________________________________________________________
C. BENDING – Carefully study the diagram on the next page before performing
the following task. Hold the ends of the glass tubing between your fingers and
rotate the tubing in the upper region of the flame while moving the tube back
and forth until the tubing is soft and pliable. While the tubing is still in the
flame, begin to bend the tubing to form a right angle. Remove the tubing from
the flame and make final adjustments to the tubing to assure a ninety-degree
bend. Do not touch the heated portion of the glass. Place the glass on a
ceramic fiber pad to cool. Repeat this procedure with the 2nd piece of tubing.
Have your teacher sign the box on the next page. Turn off burner. After
allowing the glass tubing to properly cool off, put the used tubing in the
broken glass container.
Roll and move the glass tubing back and
forth in the flame until it becomes soft.
Bend quickly and smoothly to the desired
shape and hold.
Good Bend
Poor Bends
Teacher Verification
Initials:
Date:
Bunsen Burner – Conclusion Questions
1. Label the following diagram of a Bunsen Burner
2. Which letter represents the hottest region of this Bunsen burner flame?
_____________________
A
B
C
3. What part of the Bunsen burner should be adjusted (and should the part be
opened more or closed more) if the flame:
a. is yellow?___________________________________________________
___________________________________________________________
b. is too tall?___________________________________________________
___________________________________________________________
c. is making a loud roaring noise?__________________________________
___________________________________________________________
4. Name two reasons why a yellow flame not generally used to heat glass
tubing.
______________________________________________________________
______________________________________________________________
______________________________________________________________
5. Never cool off a piece of hot glassware by putting it in cold water. Why?
______________________________________________________________
______________________________________________________________
______________________________________________________________
6. Describe why broken glassware is always placed in a special broken glass
container.
______________________________________________________________
______________________________________________________________
______________________________________________________________
7. Define “combustion”. ____________________________________________
_____________________________________________________________
_____________________________________________________________
8. Write the word equation that represents the complete combustion reaction for
any fuel.
___________ + ___________  ___________ + __________ + ______
9. Name at least 5 common appliances that generate heat and/or light via a
combustion reaction. ____________________________________________
_____________________________________________________________
_____________________________________________________________
10. Lack of which gas causes “incomplete combustion” to occur? Name and give
the chemical formula of the gas.
____________________________ ___________________________
11. Name and give the chemical formula of the toxic gas produced during
“incomplete combustion”.
_____________________________ ___________________________
12. List some symptoms of carbon monoxide poisoning: __________________
_____________________________________________________________
_____________________________________________________________
13. What two things should you do if you suspect you have CO poisoning?
_____________________________________________________________
_____________________________________________________________
_____________________________________________________________
14. How can carbon monoxide poisoning be prevented?
_____________________________________________________________
_____________________________________________________________
_____________________________________________________________
15. It is very dangerous to use a Coleman Lantern as a source of heat and light
inside a tightly closed up Camping Tent. Explain why.
_____________________________________________________________
_____________________________________________________________
_____________________________________________________________