Flame Test Lab

Chemistry Lab:  FLAME TESTS

INTRODUCTION:

When atoms of elements are heated to high temperatures, some electrons may absorb enough energy to allow them to move to higher energy levels.  The element is then said to be in the "excited state."  This excited atom is unstable, and the electrons quickly return back to their positions of lower energy or their ground state.  As the electrons return to their ground state, the energy that was absorbed is given off in the form of visible light.  The color of this light can be used to identify the elements involved.  In a flame test, the element will give off a characteristic color that serves as a simple method of identification of that element.  The color of the emitted light depends on its energy.  Blue light is more energetic than red light, for example.  When heated, each element emits a characteristic pattern of light energies, which is useful in identifying the element.

In the flame test method, a small amount of a substance is heated and the characteristic color of the substance is observed.  In this experiment you will perform a flame test on several metallic salts.  Based on your observations, you will develop a reference table that lists the flame color for each metal ion.  You will then perform a flame test on an unknown substance.  By using your reference table, you will be able to identify the unknown substance.  

PURPOSE:

1)  To observe the characteristic colors produced by metallic ions when heated in a flame.

2)  To identify an unknown metallic ion by means of its flame test.

EQUIPMENT AND MATERIALS:

            Sterno fuel                            Lab apron                              Q-tips

            Safety goggles                      Unknown solutions               Test Tubes

            Test Tube Racks

            Chloride solutions of sodium, potassium, lithium, calcium, strontium, barium, and copper.

SAFETY PRECAUTIONS:

1. LAB APRONS AND SAFETY GOGGLES ARE REQUIRED AT ALL TIMES.
2. Tie back long hair and secure loose clothing.
3. Report any spill immediately to the teacher.

PROCEDURE:

1. As you perform the experiment, record your observations in the data table below.
2. In this experiment you will rotate through various stations until you have tested all of the metallic ions listed in the data table.
3. Remove one wood splint from the solution to be tested. Place the saturated end of it into the flame and observe the color of light produced.   You will see the characteristic color only for a few seconds.  Place the wood splint back into the solution and repeat the test as many times as necessary.  Once you are sure of the color, record it in your data table.
4. Test each of the first seven compounds listed in the data table.
5. After you have tested all seven solutions, and you are sure of their characteristic colors, see the instructor to be assigned one of the unknowns. Test your unknown and determine what element it is by comparing it to the other known solutions.