FORENSIC FLAME TEST LAB CHEMISTRY Version

PRE-LAB DISCUSSION: All metal elements have distinct properties. One of these properties is its own special color when burned in an open flame. This is caused by the flame exciting the electrons of the metal element in a compound. When the electrons return from the excited state to the ground state, a photon of energy is released. Some of the energy is in our visible light spectrum, and therefore we can observe the different colors of the different metals. (The finger prints of metals) Only the metal in the compound is affected by the flame.

PURPOSE: In this experiment, you will learn to identify some metals by their special color. You must work very carefully so your chemicals remain pure.

PROCEDURE: 1. Place a small squirt of alcohol into the 100 mL beaker. 2. Place a small squirt of the station solution into the same 100 mL beaker 3. Take a lighter and light the liquid in the beaker on fire. It will burn blue for 10-15 seconds before changing color. 4. Take tongs and slightly move the beaker back and forth on the table. Do not pick the beaker up. 5. Record your results in the table, then move to another station.

DATA TABLE: Make sure you build this table in your LAB NOTEBOOK and completely fill out a line for each solution.

Compound Formula Name of the Metal Molar Mass of Compound Flame Color

Li2CO3 Pink/Red

H3BO3 Pale Green

Fe(NO3)2 Light Orange

Sr(NO3)2 Red/Orange

Ba(NO2)3 Yellow

NaNO3 Orange

CaCl2 Deep Red CuCl Neon Green

KCl Light Purple

UNKNOWN Red/Orange ANSWER THESE IN YOUR LAB NOTEBOOK

CONCLUSION QUESTIONS:

1. Based on the results of the table, what metal do you think is in the unknown?

2. KCl, CaCl2 are ionicly bonded. Show how the electrons are transferred in both of these molecules. 3. What causes the different color flames. Be specific and tell me how it works (look at your opening paragraph). 4. From past experience, what color do you think magnesium burns? 5. A fire truck arrives at the scene of an explosion at the Bohrilogical Chemical Company. The employees rushing from the building are yelling “It’s the potassium nitrate tank...hurry!” As the firemen approach the building they notice green flashes of light throughout the flame. One of the firemen remembers his high school science class doing a flame test experiment. Something about this scenario didn’t add up. What might he be thinking?

6. If you were going to a fireworks show and you see a firework that is red, what chemical was used in the fireworks?

7. Use the knowledge you have gained from the table, you need to design and build a firework that contains three different colors. Write down what colors you will use, and what order they will explode. Then use the diagram below to show what chemicals will be placed where in the firework?