University:
High School
Course:
High School Chemistry
Academic year:

2022
Views:

123

Pages:

2
Author:

5CelestialChronicle

Name ___________________ Period ____ Activity- Flame Tests ALWAYS wear goggles when working in the laboratory! Background: Many elements produce flames of a characteristic color when they come in contact with the flame of the Bunsen burner. Using these “flame tests”, scientists can determine the identity of an element based on the unique color pattern released by an element. How it works: By placing atoms into a flame, electrons can absorb energy and jump to an excited (higher) energy state. When they return back down to their ground state they release that energy by giving off/ emitting a photon of light. The amount of energy in the photon of light emitted determines its color (red = lowest energy visible light & violet = highest energy visible light). A spectroscope would allow us to fully see the full spectrum of colors being released, instead of just one color, but the flash of light occurs too quickly to use these devices in this lab. Because each element has a unique electron configuration, the electrons will “jump” up and fall back down in a unique pattern for that element. Purpose: To observe how the atomic structure of an atom influences its color when burned. Procedure: 1. Your instructor will provide test tubes containing the salts that you need. Enough DISTILLED water should have been added to make thick slurry in your test tube. You can add small amounts of distilled water to the test tube if needed using the squirt bottles in your bin. 2. Dip a wooden splint into the slurry then insert it into the flame. Record your results in the data section. Be sure to include such details as whether or not a color is slow in appearing. Repeat the above steps until you have identified the flame color of these substances. 4. When you have successfully completed the identification of the known elements, proceed to identifying the unknowns. You will find 2 unknowns in the front of the class. Data and Observations: Name of Substance Calcium chloride Results of the flame tests: Formula Testing Color of Flame and Notes CaCl2 Ca Sodium chloride NaCl Na Strontium Chloride SrCl2 Sr Manganese chloride MnCl2 Mn Copper Sulfate CuSO4 Cu Potassium carbonate K2CO3 K Potassium chloride KCl K Lithium nitrate LiNO3 Li Unknown A Tests on the unknowns: Color of flame observed Identification ? B Calculations/ Analysis: 1. What happens to an electron when energy is added? 2. Why do atoms release light when they are heated? 3. What determines the frequency (color) of light released from an atom? 4. Why is the color for a specific atom unique to that element? Questions for Discussion: 1. Sodium atoms give off a yellow/orange colored flame when heated. Does this mean that all substances that give off a yellow/orange flame when heated contain sodium? Explain your answer 2.. Hydrogen has only 1 electron. Explain why a hydrogen atom will have multiple colored bands on the spectroscope. You may draw a picture to aid in your explanation. 3. Explain how knowledge of flame tests would be useful to a fireworks designer.