Laboratory Experiment: Flame Test

Laboratory Experiment: Flame Test

Question: When a compound is placed in the flame of a burner, what happens to the color of the flame and what causes this to occur?

When chemical compounds are heated, they gain energy. The electrons in some of these chemicals will jump from their ground state electron configuration (such as the electron configurations we have been drawing for the elements) to higher energy levels. As these electrons fall back to their original positions in the atom, they emit energy. One form of this energy is light energy. This is what you will be observing in this experiment.

Materials required:

Chemicals used in experiment

2Test tube per chemical for solid chemical and cleaning water

Nichrome wire wand

Tirrel burner

Striker

Goggles

Procedures

Safety: Wear goggles at all times. If you want to remove them to write in your notebook you may sit at a table in the center of the room. When you sit down remove them and when you stand up put them on. Use aprons. Pull back hair. No loose clothing. Close-toed shoes. NO FOOLING AROUND

It is very important that you DO NOT mix up the nichrome wire wands.

Watch Demo before you begin

1. Work in teams of two

2. At each table there are two samples and two tirrel burners and matches. Start the burner as you have learned to do and obtain a low blue flame with the inner blue flame.

3. Next take the nichrome wire and place in the flame. Notice its color when it becomes red hot. This is not the color of the flame you are looking for. The flame to observe is the one obtained just as you place it in the flame.

4. Place the wand in the test tube with the solution of the compound, quickly place it in the flame and observe its color. Write down the color and any observations on the table provided below. Do this no more than three times. 5. Return the nichrome wire to the solution test tube. When this is completed, exchange chemical compound setups with you tablemates.

6. Repeat the procedure for each chemical compound.

7. When you table is done with both chemical compounds, pass them both clockwise to the next table.

8. When all chemical setups are complete, the class will discuss which chemical compounds that you would like to observe again.

Flame Test Data - Table 1
Compound / Color&Shape / Observation

Categorize the results by metals and anions

Flame Test Results-Color
Anions / Chloride / Sulfate / Nitrate
cations / Ba Barium-Exp
Actual
Ca Calcium-Exp
Actual
Co Cobalt-Exp
Actual
Cu Copper-Exp
Actual
K Potassium-Exp
Actual
Na Sodium-Exp
Actual
Sr Strontium-Exp
Actual

Add: Lithium Chloride

Questions:

1. Is it the metal or the chloride, sulfate and nitrate that controls the color? Use evidence from Table 2

2. Explain why the compounds are changing color in the flame? Use energy, energy levels, the Balmer series, excited state, ground state and emission to explain.

3. What is an atomic spectrum? What scientist discovered this? Why is it important?

For #3 and #4 research on the internet and copy atomic emission spectra into your report

4. Diagram the Visible spectrum

5. Diagram the Atomic Spectra of the eight elements ( metal cations) in the table above and then explain the difference between the flame test of these and the atomic spectrum.

Write Conclusion, follow the “Writing a Conclusion” instructions.