Flame Test: Red, Green, Blue, Violet?
Flames from a Bunsen burner can appear different colors from the visible light spectrum.Copyright 2005 Arthur Jan Fijalkowski, Wikimedia Commons http://commons.wikimedia.org/wiki/File:Bunsen_burner_flame_types.jpg
To become familiar with the transfer of energy in the form of quantum, students perform flame tests, which is one way chemical engineers identify elements—by observing the color emitted when placed in a flame. After calculating and then preparing specific molarity solutions of strontium chloride, copper II chloride and potassium chloride (good practice!), students observe the distinct colors each solution produces when placed in a flame, determine the visible light wavelength, and apply that data to identify the metal in a mystery solution. They also calculate the frequency of energy for the solutions.
Before beginning to design a solution to a problem, engineers must research the concepts involved. As part of their research, chemical engineers use the flame test to identify an element based on the color it emits when placed in a flame—a low-tech and reliable method of identification. This unit's challenge question includes aspects of environmental engineering (effect of pollution on the Earth's ozone layer and consequences to public health) and biomedical engineering (use of nanoparticles in medical technologies).
After this activity, students should be able to:
- Explain that energy received by electrons to move them to an excited state is quantized.
- Explain that some wavelengths of light are in the visible light range while others are not, but nonetheless can cause chemical reactions.
- Calculate the number of grams of three ionic salts needed to make the appropriate molarity of solution.