The Learning Objective
When students study the chemical composition of mixtures and substances used in lab experiments, color absorption and emission are important components of that study. What they understand is that mixtures are composed of a combination of metals that have a signature color when exposed to flames.
In this lab, students will identify the color fingerprints of a number of unknown metals using the flame test. If a student decides to become a CSI investigator or a forensic pathologist, identifying the fingerprints of substances at the crime scene can prove invaluable in solving the case. In addition, if a student decides to become a Supervisor in the paint department at Home Depot, understanding the dynamic mixture of metals can solve the case of mixing the perfect fuchsia or crimson color in making a room vibrant or a painting disaster.
Let the Lab Begin
1. Make sure that all lab materials are at the lab desk before beginning the experiment. Do not leave flames unattended. Mark 25 ml beakers containing standard solutions provided by the instructor.
2. Using the tong take a tongue depressor and dip it into a known standard solution indicated in the data chart. Put the depressor in the outer blue flame of the Bunsen burner or other fire apparatus supplied by your instructor.
3. Observe for a color fingerprint and make sure that you remove your depressor before it begins to burn. The first flash of color when the solution hits the flame is the color absorption of the solution.
Recording the Results
Record your data in the data table in your notebook. Use the following headings for both data tables:
Table 1: Standard Solutions
Metal/ Color of flame observed/ Actual color of flame (from flame color chart)
Table 2: Unknown Solution
# of Solution/ Color of flame observed/ Metals identified in unknown (use Table 1’s data to figure this out)
Clean up your lab area after you have completed the lab.
The Learning Analysis and Reflection
In summarizing the lab results, students can answer the following questions in their lab journals to further process the learning experience:
1. What is the identification of the metal in your unknown solution?
2. Why is important to expose the solution to the blue part of the flame?
3. What would be the result if solid metals were used instead of solutions?
4. Reflect on your data and think about what additional solutions could be used to test for metals using the flame test.