October 29, 2008

Heather HermanGroup: Jackie, Sarah, and Daniel

Purpose: To perform flame tests on several metallic ions and use the results to identify an unknown substance.

Hypothesis: If I perform flame tests on metallic ions and record the observations, then I will be able to identify an unknown substance.

Materials:Wooden splints soaked in cation solutionsLab burnerBeaker filled with water

Procedure:1. Place soaked splint in the burner flame and record the color of the flame. Place

the tested splint into a beaker of water and repeat with the other splints.2. Dispose of materials as directed by a teacher.

Metallic Ion Color of FlameCa2+ Orangey redLi+ FuchsiaCu2+ Turquoise greenNa+ Light orangeK+ LavenderSr2+ OrangeBa2+ Spring greenX Light green

Questions: 1. The flame test indicates the amount of energy being used or released among the

electrons when the color changes. Different flame colors signify different amounts of energy being released.

2. When a metallic ion is heated in a flame test, the electron jumps to a higher energy state. When it returns to the lower energy state, energy is emitted as visible light. The color differs depending on how much energy is released, so there is a characteristic color for each ion.

3. Increasing wavelength: (lowest) a. Gamma Raysb. X raysc. Ultraviolet raysd. Visible rayse. Infrared raysf. Microwavesg. Radio waves (highest)

In the visible spectrum, the wavelengths range from 400 nm to 700 nm. Violet has the shortest wavelength.

4.

5. Metallic salts are used in fireworks because in salts, electrons move to higher energy states, and when they return to a lower energy state, light energy is released. They are metallic because metals burn in different colors, producing the bright fireworks.

Fireworks Questions:

1. Color is produced similarly in fireworks to the way it is produced in flame tests. In flame tests, holes allow oxygen to enter the burner and electrons release light energy, resulting in different colors depending on the compound. Fireworks also begin with an oxygen source and have packed compounds in cardboard shells that produce bright colors as well.

2. The colors produced by the compounds in the table do correspond with my data results in the flame test lab. The copper in the flame lab turned turquoise, and the table says that copper compounds are used to make blue. Also, in the flame test lab, barium turned light green, and the table says that barium compounds are used to make green.

3. The time-delay fuse creates the color displays in fireworks because the colors start when the flame reaches the substance, which is controlled by the time-delay fuse.

Conclusion:The unknown substance was identified as barium because it turned to a similar

shade of light green that barium did. A possible source of error was that the colors are similar and hard to distinguish from one another.

Extra Credit:

Cesium and Rubidium were two elements discovered with the spectroscope by Robert Bunsen and Gustav Kirchoff. Modern spectroscopes are now controlled by computers, and some of the parts are also used to capture light in photographic film. Spectroscopes are important scientific tools used to analyze unknown substances and for studying astronomy.