Bunsen burner Lab

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Chemistry Lab
Getting to know your Bunsen burner
Part I
The Bunsen or Tirrell burner is commonly used in laboratory heating operations. While 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 an adjustable opening or ports in the base of the barrel to introduce
air into the gas stream. The burner may have an adjustable needle valve to regulate the supply of gas, or
adjusting the valve on the supply line may regulate the gas supply simply. The burner is always turned off
at the gas valve, never at the needle valve.
Take your burner apart and examine it. Compare the parts with the drawing in Fig. 1-1.
Put the parts together again and note
particularly how you can control the amount of
air admitted near the base of the burner. In
lighting the burner, partially close the ports at the
base of the barrel, turn the gas full on, and hold
the lighted match about 5 cm above the top of the
burner. If you are using a torch lighter place the
torch lighter next to and slightly above the
burner, apply a downward pressure of the flint
towards the plate and strike the lighter.
The gas may then be regulated until the
flame has the desired height. If a very low flame
is needed, the ports should be kept partly closed
when the gas pressure is reduced. Otherwise the
flame may "strike back" and burn inside the base
of the barrel. If this happens, turn off the gas,
decrease the amount of air admitted, and re-light.
Part II
LUMINOUS FLAME
Relight the Bunsen burner. Close the airports or inlets as completely as possible and note the color and
shape of the flame which is now luminous.
A
Pass your hand quickly through the flame, which can be done without discomfort.
B
Using crucible tongs, hold a dry porcelain-evaporating dish in the flame for a few seconds.
Examine the dish and record your observations. After the dish cools, clean and dry the
evaporating dish.
C
Sketch the luminous flame and show its structure as far as you can see.
D.
2
Using a test tube holder, hold one end of a glass tube about 15 cm long and inclined at a 45
degree angle just inside the barrel and attempt to light the gas which escapes from the other
end of the glass tube. If unsuccessful with lighting the gas at the end of the glass tube, then
increase the flow of gas slightly and try again. Record your observations.
F
Extinguish the burner flame.
Part III
NON LUMINOUS FLAME
For laboratory work, you should adjust the burner so that the flame will be free of yellow color,
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. Slowly open the airports and
notice that the flame loses its luminosity and two well-defined
regions appear in the flame. The two distinct regions of the flame
are called the oxidizing and reducing regions. This is the so-called
Bunsen flame, and it should always be used for heating purposes.
You may have to adjust the amount of air admitted and the amount
of gas mixing with the air. A yellow flame yields much light but
little heat. Such a flame is the mark of an amateur. Obtain a flame
which is quiet, steady, and does not go out.
A
Insert a wooden splint in the reducing region across
the flame near the base of the blue inner region, resting on the top of the barrel for a few
seconds. Remove from the flame, extinguish, examine and record observations.
B
Repeat the process, but place the splint one cm above the oxidizing region.
C
Using tongs, hold a cool, dry porcelain-evaporating dish above the top of the reducing
region for about ten seconds. Do not permit the evaporating dish to incandesce. Remove
from the flame, place on a wire gauze, and allow the dish to cool. Then examine and
record your observations.
D
Repeat the above process, but place the dish above the top of the oxidizing flame.
E.
Diagram the non-luminous flame and show its structure.
F
Hold one end of a glass tube inclined at a 45-degree angle in the inner cone of the Bunsen
flame, just above the barrel opening, and attempt to ignite any gas escaping from the other
end of the glass tube. Record observations.
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Part IV
TEMPERATURE OF PARTS OF THE BUNSEN FLAME
The approximate temperatures at different parts of the flame can be determined by observing the color of
a copper wire held in the flame. If the color is faint red the temperature is about 500 degrees Celsius; if
the color of the wire is dark red its temperature is about 650 degrees Celsius; and if the color is orangeyellow the temperature is about 900 degrees Celsius.
A
Obtain a 10 cm piece of copper wire and hold it using crucible tongs. Place the tip of the
wire in the flame for two seconds and estimate the temperature at the corresponding point
on your diagram of a Bunsen flame. Repeat this process at five to 10 widely separated
points of the flame.
B
Obtain another piece of copper wire, place in the reducing cone, (use forceps;), and lift it
slowly up into the oxidizing cone. Keep it in this cone for a few minutes. According to the
"Handbook of Chemistry and Physics" the melting point of copper is 1083 °C.
C
Turn off your burner. Obtain a match and a piece of wire, at the mid-point of the wire
make a loop and place the match in the loop. Place the match into the barrel supported by
the wire. Relight the burner and record observations.
D
Using tongs, slowly lower a piece of wire gauze which is held horizontally into the flame
of a Bunsen burner until the gauze rests on the top of the barrel. Raise the gauze slowly.
Allow the gauze to cool and repeat, lowering the gauze quickly. Try to 'pick up' the flame
by slipping a cool gauze under the flame at the top of the barrel. Record observations.
Lab Report Format
Title
Introduction
Procedure
Equipment List
Table of Observations
Conclusions and Answer Questions
Lab Report Questions:
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2.
3.
4.
5.
6.
7.
8.
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10.
11.
12.
How would you describe the flame in Part II? Draw a picture of the flame.
How would you describe the flame in Part III? Draw a picture of the flame.
The flame in Part II is seldom used in the laboratory. Why? What happened to the bottom
of the evaporating dish? What do you think the substance is on the bottom of the
porcelain?
What are the three requirements for combustion.
Under what conditions do we have complete combustion and incomplete combustion?
Is there a minimum temperature at which a fuel will burn? What is this temperature
called?
What is the difference, if any, between flash point and kindling point?
Why is your hand not burned in the luminous flame?
Write an equation to account for the formation of the deposit.
Where is the hottest part of the Bunsen flame? Why is this particular region the hottest?
Where is the coolest part of the Bunsen flame? Why is this particular region the coolest?
Write a short paragraph on the history of the Bunsen Burner or any other type of laboratory
burner.
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