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Hon Unit 2 Lab Bunsen Burner and Flame Test

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Hon Unit 2 Lab Bunsen Burner and Flame Test Powered By Docstoc
					The Bunsen Burner


In the science laboratory, one of the most common ways of heating objects is by
using the Bunsen burner. Other styles of gas burner include the Tyrrell burner
and the Meeker burner. Each is named for the scientist who developed it,
and each has its own advantages. Our class has the Tyrrell style of burner. In
spite of this, the term "Bunsen burner" is commonly used in a generic fashion
for almost any gas burner in a chemical laboratory. Open flames must be used
with extreme caution - open flames are hardly ever used in labs involving
chemicals which can burn.

Purpose: In this exercise we are investigating the operation of our Tyrrell
burners and the characteristics of the flames they produce.

Safety Precautions: Because of the danger involved with flames, safety rules
must be followed with extreme care

1. Remove any flammable objects from the immediate work area.

2. Do not place the burner where it will burn a cabinet or shelf above it.

3. Objects that have been heated can remain hot for a long time. Be sure you
   have allowed sufficient time for such objects to cool down before touching
   them or putting the in contact with flammable materials.

4. Safety goggles must be worn for this experiment. Loose hair must be
   restrained.

Operating notes:

The gas valve on the bench is off when turned to either side, and on when the
handle is straight out.

The knurled knob on the bottom of the burner controls gas flow, making the flame
bigger or smaller.

Turning the barrel of the burner opens or closes slots which admit air, making
the flame hotter or cooler.

Procedure:

1. Put on the safety goggles.

2. Securely connect the Bunsen burner to the gas outlet using the rubber tubing.

3. Turn the gas adjustment screw on the bottom of the burner clockwise gently
   until it stops turning. (Clockwise, if you are looking at the bottom of the
   burner - righty tighty, lefty loosey.)

4. Now unscrew the valve (turn counter clockwise) 2 complete turns.

5. Light the burner as follows:

• With the striker (or a lit match) in one hand, turn on the gas at the table
with the other. You must have your ignition source ready to avoid releasing
large amounts of gas into the lab, which would be an explosion risk and
unpleasant to breathe.

• Place the cup of the striker facing downward over the opening of the barrel
  and strike one or twice to ignite the flame. (Of course if using a match, the
  burning match need only be placed in the gas stream from the side.) - Note –
  pushing the striker unnecessarily seems fun - making lots of pretty sparks,
  but it is wasteful - don't do it.

• Adjust the flame so it is 2 - 3 inches high by changing the amount of gas (the
  knob on the bottom). A yellow flame indicates too little air, allowing some of
  the carbon in the fuel to remain unburned. Adjust the air intake by turning
  the barrel of the burner. A hot flame is blue. If the flame is blue but blows
  out, reduce the amount of air by turning the barrel to close the slots at the
  base.


• When turning off the burner always turn it off at the main valve at the table.
  Never try to blow it out.

6. Holding a length of wire by a cork, use the wire to observe the hot areas of
   the flame. Hold it for a few seconds in the flame at the bottom, then the
   middle, and then at the top of the inner blue cone of fire. The wire will
   glow red hot where the flame is hottest. Record you observations with
   diagrams.

7. Turn off the burner and allow it to cool down, while you do the following:

• Push a straight pin through a wooden match. It should be below, but near, the
  head. The best way to do this is put the pin in lightly, then put the head of
  the pin on the bench and push down on the ends of the match, being careful
  that where the pin is going to come through the match stem is NOT pointing
  into your finger! If unsure, check with your teacher!

• Place the match in the center of the barrel supporting it by the ends of the
  pin, with the match head up.

• Follow the above procedure to relight the burner, but stay away from the
  suspended match head.

• Observer the match in the burner. What can you conclude about this portion of
  the flame?

• After a short time, use the wire on the cork to nudge the pin so the head of
  the suspended match touches the inside bottom of the outer cone (blue part) of
  the burner flame. Notice what happens.

Conclusions: From your observations, describe where the flame of a Bunsen burner
is hottest. Then describe where it is the coolest. How can you make a flame
hotter?
LAB: Flame Tests                        Name____________________________________


PURPOSE: To become familiar with a procedure known as flame tests, and to
identity certain elements by the color of flame they produce.

BACKGROUND: There are certain metals that can be recognized by the color they
give to a flame. When the electrons in outer energy levels are excited enough by
energy from a suitable source, they are raised to higher energy levels. When
they return to their normal levels, the absorbed energy is released in the form
of light. The released right has a special spectrum, or color pattern, specific
to a certain element. No two elements have the same spectrum. The outer energy
level electrons of Group 1 elements are easily excited by a gas flame. Several
Group 2 and transition metal elements are also easily excited by the same
technique. These elements give a distinct color to the flame.

MATERIALS: Tyrrell burner, Q-tips, each saturated with one of the following
solutions: lithium chloride, copper chloride, calcium chloride, strontium
chloride, barium chloride, potassium chloride, sodium chloride. A set of
unknowns solutions.


PROCEDURE:

1. Construct a neat data table which will include the metal names and the flame
   colors you observe.

2. Put on your safety goggles.

3. Light the burner. Adjust if necessary. Flame should be blue.

4. Hold a Q-tip that is saturated with the solution in the hottest part of the
   flame. It may take a few seconds for the solution to become hot enough to
   show a color. Record the color of the flame on your data table.

5. Repeat this process with each of the unknowns. Add the information on the
   unknown - it's identifying letter and the color of its flame - in your data
   table. Then add a column in which you attempt to identify the ion responsible
   for that flame color – what’s present in the solution?

QUESTIONS:

   1. Chemical compounds have two parts: the cation (frequently a metal) and the
      anion. In today's solutions the anions are chloride. Is the flame color a
      test for the metal or the chloride in each compound? Explain your answer.

				
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