Name_____________________________________ Period_____ Date_____ Flame Tests for Metals Lab Purpose To observe and identify metallic ions using flame tests. Introduction ; The characteristic yellow of a candle flame comes from the glow of burning carbon fragments. The carbon fragments are produced by the incomplete combustion reaction of the wick and candle wax. When elements, such as carbon, are heated to high temperatures, some of their electrons are excited to higher energy levels. When these excited electrons fall back to lower energy levels, they release excess energy in packages of light called photons, or light quanta. 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 for identifying the element. The characteristic colors of light produced when substances are heated in the flame of a gas burner are the basis of flame tests for several elements. In this experiment, you will perform the flame tests used to identify several metallic elements. Materials 5 cotton swabs 5 solutions pencil or pen Goggles lab apron Bunsen burner Procedure BEFORE DOING THE LAB, ANSWER THE PRE-LAB QUESTIONS 1. Obtain the solutions containing the metal ions from your instructor. 2. Put on the safety gear and light the Bunsen burner. 3. Dip a cotton swab into the solution you are going to test and then place it in the edge of the flame. Note the color of the flame in the data table below. NOTE: Don’t leave the cotton swab in the flame long enough to burn it. 4. Do the same thing for the other solutions. Pre-Lab Questions: Answer the following questions to make sure you understand the background information. 1. What did Earnest Rutherford’s gold foil experiment demonstrate about the composition of an atom? 2. What happens to an atom’s electrons when exposed to excess energy? 3. What is released when an atom’s electrons lose energy and return to its ground state? DATA TABLE Solution Color when heated Lithium Chloride LiCl Copper Chloride CuCl2 Strontium Chloride SrCl2 Sodium Chloride NaCl Potassium Chloride KCl Analyses and Conclusions: 1. Why did different chemicals emit different colors of light? 2. Why do you think the chemicals had to be heated in the flame for the colored light to be emitted? 3. Using what you know about wavelengths, frequency, and energy, list the metallic elements used in the flame test in increasing order of the energy of the light emitted. 4. How does the flame test provide support for quantized energy levels? Explain your answer.
Pages to are hidden for
"Lab Flame Test for metals"Please download to view full document