Using a Bunsen Burner and Heating
Learning Objectives
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
To observe and use the proper safety technique for the Bunsen burner.
To understand the temperature differences between a yellow and blue flame.
Introduction
The best way to become familiar with chemical apparatus is to actually handle the
pieces by yourself in the laboratory. In this experiment, you will learn how to
adjust the gas burner. Great emphasis is placed on safety precautions that should
be observed whenever you perform an experiment and use this apparatus
Safety
Take the necessary safety precautions before beginning this experiment. Wear
goggles and get into the "good habit" of always putting on this standard safety
equipment as soon as you enter the lab. It is important that you and your partner
observe precautions while conducting experiments.
Materials
Heat-resistant mat
Forceps
Matches
Test Tube
Beaker
Wire Gauze
CuSO4
Test Tube Holder
Burner and tubing
Evaporating dish
Copper wire, 18 gauge
Recording Your Observations
Record your observations in your journal.
Discussion
The Bunsen or Tirrell burner is commonly used as a source of heat in the laboratory.
Although the details of construction vary among burners, each has a gas inlet located in
the base, a vertical tube or barrel in which the gas is mixed with air, and adjustable
openings or ports admit air to the gas stream. The burner may have an adjustable needle
valve to regulate the flow of gas. In some models, the gas flow is regulated by simply
adjusting the gas valve on the supply line. The burner is always turned off at the gas
valve, never at the needle valve. Look at Figure 1 as you examine your Bunsen burner
and locate these parts.
Caution: Before you light the burner, check to see that you and your partner
have taken the following safety precautions against fire: Wear safety goggles.
Confine long hair and loose clothing: Tie long hair at the back of the head
and away from the front of the face, roll up long sleeves on shirts, blouses,
and sweaters away from the wrists. You should also know the locations of
fire extinguishers, fire blankets, safety showers, and how to use them in case
of a fire.
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In lighting the burner, partially close the ports at the base of the barrel, light a match and
turn the gas full on. The gas flow may then be regulated by adjusting the gas valve, until
the flame has the desired height. If a very low flame is needed, remember that the ports
should be partially closed when the gas pressure is reduced. Otherwise the flame may
burn inside the base of the barrel. When improperly burning in this way, the barrel will
get very hot, and the flame will produce a poisonous gas, carbon monoxide.
Caution: Carbon Monoxide is a poisonous gas. If the flame is burning inside
the base of the barrel, immediately turn off the gas at the gas valve. Do not
touch the barrel, for it is extremely hot! Allow the barrel of the burner to
cool off and then proceed as follows:
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Heating a liquid in a test tube. The correct procedure for heating liquids in the
laboratory is important to laboratory safety.
1. Adjust your gas burner to give a gentle blue flame.
2. Fill a test tube one-third full with the liquid to be heated.
3. Grasp the test tube with a test tube holder near the upper end of the tube.
4. Hold the test tube in a slanting position in the flame, and gently heat the tube a short
distance below the surface of the liquid (Figure 2).
5. Shake the tube gently as it is being heated, until the liquid boils or reaches the desired
temperature.
Caution: Never point the open end of a test tube you are heating either toward yourself
or anyone working nearby. Never heat the bottom of the test tube.
Heating a liquid in a beaker. Many laboratory experiments require
the use of a hot-water or boiling water bath. This procedure describes how to assemble a
water bath.
1. Fasten an iron ring securely to a ring stand so that it is about two to four centimeters
above the top of a gas burner placed on the ring stand base.
2. Place a 250-mL beaker one-hall filled with water on a wire gauze resting on the iron
ring (Figure 3).
3. Light your gas burner and adjust it to give a hot flame.
4. Place the burner beneath the wire gauze. For a slower rate of heating, reduce the
intensity of the burner flame.
Caution: Never heat plastic beakers or graduated glassware in a burner flame. Never let
a boiling water bath boil dry; add water to it as necessary.
How to Heat Material in a Test Tube
1. Check to see that the test tube is PYREX or a similar heat-resistant type.
2. Always use a test tube holder or clamp when heating the test tube.
3. Never point a heated test tube at anyone, because the liquid may splash out of the test
tube.
4. Never look down into the test tube while heating it.
5. Do not heat any one spot on the test tube. Heat the test tube from the upper portions of
the tube downward and continuously move the test tube. Otherwise pressure from a
vapor meeting a layer of liquid above it may cause the bottom of the tube to blow out.
Figure 2. Heating a liquid
in a test tube.
Figure 3. Heating a liquid in a beaker.
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Pre-Lab Questions
After reading the techniques and procedures, answer the following questions in your
journal.
1. What does a properly adjusted flame look like?
2. Where is the gas valve located on the Bunsen burner?
3. Where should the test tube be pointed when it is being heated?
4. When heating a solid in a test tube, where should you start heating?
5. How far should the ring be fastened above the top of the gas burner?
Procedure
While doing the following procedures, answer the questions (in bold) in you lab journal.
1. Turn the gas full on and then light the burner. Control the height of the flame by
adjusting the gas valve. By taking these steps, you should acquire a flame that is
burning safely and is easily regulated throughout the experiment. There will be a
visible blue cone inside the flame. (See Fig. 1) Have Mr. Richardson check you
flame.
2. Screw the barrel of the burner in a clockwise fashion completely closing the holes
(ports) at the base of the burner.
3. Q1: What is the result?
4. Using the forceps, hold an evaporating dish in the tip of the flame for about one
minute. Place the dish on a heat-resistant mat, allow the dish to cool, and then
examine its underside.
5. Q2: Describe the results and suggest a possible explanation.
6. Such a flame is seldom used in the laboratory. For laboratory work, you should
adjust the burner so that the flame will be free of yellow color, non-luminous, and
also free from the "roaring" sound caused by admitting too much air. Regulate the
flow of gas to give a flame extending roughly 8 cm above the barrel. Now adjust the
supply of air until you have a quiet, steady flame with a sharply defined, light blue
inner core. This adjustment gives the highest temperature possible with your burner.
Using the forceps, insert a 10-cm piece of copper wire into the flame just above the
barrel. Lift the wire slowly up through the flame.
7. Q3: Where is the hottest portion of the flame located?
8. Hold the wire in this part of the flame for a few seconds.
9. Q4: What is the result?
10. Q5: Why is the non-luminous flame preferred over the yellow luminous flame in
the laboratory? (Hint: The melting point of copper is 1083 degrees Celsius.)
11. Grab a test tube and put about 2 cm of CuSO4 into it.
12. Q6: Describe the appearance of the CuSO4.
13. Following the steps on the previous page, heat the test tube for a few minutes until the
reaction has completed.
14. Q7: List two observations and describe the appearance of the CuSO4.
15. Set up an apparatus for heating liquid in a beaker (Figure 3).
16. Measure 100 mL of water and pour into the beaker. Measure the water’s temperature.
17. Following the steps on the previous page, heat the water for five minutes.
18. Q8: What is the temperature of the water after five minutes? How much of a
temperature change was there?
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