mini LAB 5

= Flame Tests

Have you ever wondered what gives fireworks their colors? Atoms in the fireworks are excited by being heated, causing their electrons to move into higher energy levels. Atoms do not stay excited for long, however; their electrons move back to their normal energy levels, releasing the extra energy as electromagnetic energy. If this energy is in = the visible region of the spectrum, we see it as colored light.

Atoms of each element have uniquely different el= ectron arrangements. Therefore, as their electrons fall back to normal energy leve= ls, they release energy in the distinctive patterns known as emission spectra. Since each element emits a unique set of wavelengths, emission spectra and their colors can be used to identify the elements. In this experiment, you = will observe the flame colors characteristic of two elements and will use the co= lors to trace the path of these elements in a chemical reaction.

Objective: To classify certain compounds, by the distinctive color they emit when hea= ted in a flame. The color of the emitted light can be used to identify the compound.

Materials: Bunsen burner; cotton swabs (15); distilled water; crystals of lithium chloride, s= odium chloride, potassium chloride, calcium chloride, strontium chloride, cupric = chloride, sodium nitrate, potassium nitrate, calcium nitrate, strontium nitrate, lith= ium nitrate, cupric nitrate and barium nitrate, unknown

Hypothesis:

Procedure

1. Dip the cotton swab into the lithium chloride so that the cott= on is saturated. Put the swab into the flame of a Bunsen burner. Observe the c= olor of the flame and record it in the data table. Dispose of the burned swab in= the waste beaker.

2. Repeat step 1 for each of the metallic chlorides (sodium chlor= ide, potassium chloride, calcium chloride, strontium chloride and cupric chlorid= e). Be sure to record the color of each flame in your data table. Dispose of the burned swab in the waste beaker.

3. Repeat step 1 for each of the metallic nitrates (sodium nitrat= e, potassium nitrate, calcium nitrate, strontium nitrate, lithium nitrate, cup= ric nitrate and barium nitrate). Be sure to record the color of each flame in your data table. Dispose of the burned swab in the waste beaker.

4. Obtain a sample of unknown crystals from your teacher. Repeat = the procedure in step 1 using the unknown crystals. Record the color of the fla= me produced by the unknown crystals in the data table. Dispose of the burned s= wab in the waste beaker.

5. Dispose of used cotton = swabs as directed by your teacher. (Put in red flame proof can located at front of room.)

Observations

Flame test results=

Compound	Flame color
Lithium chloride
Sodium chloride
Potassium chloride
Calcium chloride
Strontium chloride
Cupric chloride
Sodium nitrate
Calcium nitrate
Potassium nitrate
Strontium nitrate
Lithium nitrate
Cupric nitrate
Barium nitrate
Unknown

Analysis

1. Each of the known compounds tested contains chlorine or nitrogen, yet each compo= und produced a flame of a different color. Explain why this occurred.<= /p>

2. How is the atomic emission spectrum of an element related to these flame tests?=

3. What is the identity of the unknown crystals? Explain how you know.

Flame Test Results=