SURVEY OF CHEMISTRY LABORATORY I CHEM 1151L FLAME TESTS

CAUTION!!! BE SURE TO WEAR SAFETY GLASSES AT ALL TIMES IN THE LABORATORY NO EXCEPTIONS TO THIS RULE!

- To explore the line spectra of a variety of elements by heating them in a Bunsen burner flame - The data gathered from the flame colors created by the elements will be used to identify some elements present in unknown solutions FLAME TESTS

- Electrons in atoms, ions and molecules are restricted to specific energy levels - An electron “excited” by some outside energy (flame or electricity) moves from its present energy level to a higher energy level - A photon of light is produced as the electron falls back to its ground state - The light given off is of a specific color since it has a specific wavelength or frequency of light associated with it FLAME TESTS

- A glass prism can be used to identify the various “lines” produced by the photons - The various photons bend differently as light passes through a prism depending upon their wavelength (or frequency) - The smaller the wavelength the greater the bending or diffraction and vice versa FLAME TESTS

- Light the Bunsen burner BUNSEN BURNER

- Hold the platinum wire in the flame until it is clean - Position the wire loops at the tip of the blue cone of the flame until little or no color exhibit by the flame BUNSEN BURNER

- Place several drops of the solution to be tested in the small crucible dish supplied DROPS OF SOLUTION

- Hold the crucible near the air intake of the Bunsen burner SAMPLE VAPORIZATION Click here to watch video

- Plunge the hot wire into the crucible - Sample will be vaporized and carried up the burner and into the flame - Observe and record the color emitted SAMPLE VAPORIZATION Click on picture to watch video

- Move to a new location for the next flame test - The burners and wires stay in one location - Be sure to observe all of the seven known samples and the five unknown samples - Match the colors to identify the unknown samples IDENTIFICATION OF UNKNOWNS