Flame Test Lab
A flame test is a process used by scientists to indicate the presence of metal atoms. Specific elements will burn a unique color. For example, the periodic table element Boron burns green. These element specific colors are recorded as an emission spectrum. The emission spectrum is the color(s) released when electrons from an atom are excited to a higher energy level. The color is released as the excited electron transitions from excited state to normal energy state. In that downward transition, energy is released as light.
Na 1s22s22p63s1 ground state configuration
Na 1s22s22p63s03p1 excited state configuration
In the electron configuration above, as the excited 3p1 electron falls downward to ground state 3s1 position, the extra energy is released in the form of a bright yellow orange color.
In this lab, you will perform the flame test, record the color observed, and calculate the amount of energy each substance released when the atom transitions from excited state to ground state. You will then analyze the relationship between wavelength and energy released.
PROCEDURE:
1. Light Bunsen burner. 2. Obtain a wire loop. 3. Add 1 drop of calcium chloride to the wire loop. 4. Hold the chemical end of wire look over the Bunsen burner, near tip of small, inner, blue flame. 5. Record in data table the flame color observed. 6. Repeat steps 2 through 7 with 4 other chemicals 7. Turn gas valve off to extinguish Bunsen burner. 8. Clean up work area and wash hands.
Which compound released the most energy? WHAT IS THE RELATIONSHIP BETWEEN WAVELENGTH AND ENERGY THE LONGER THE WAVELENGTH, THE ______ENERGY RELEASED?
DATA TABLE:
FIGURE 1: flame color and energy changes data
ENERGY Metal Flame color WAVELENGTH WAVELENGTH CHANGE (J) (nm) (m) E Calcium Chloride CaCl2 Copper Chloride CuCl2 Lithium Chloride LiCl Potassium Chloride KCl Strontium Chloride SrCl2 Sodium Chloride NaCl
POST LAB CALCULATIONS:
1. Use the poster in back of classroom, or projected image in front of classroom, or use the internet to estimate the wavelength in nanometers for each color observed.
2. Convert wavelength in nanometers to meters. Show all work on a clearly labeled separate page. Record new values in data table. 1 meter = 109 nanometer
wavelength nm x 1 m = wavelength m 109 nm
3. The characteristic color of the flame is due to two closely spaced energy transitions. Use the following equation to calculate the average energy change (E) corresponding to the observed flame color for each metal. Show all calculations on a clearly labeled separate page. Record results in the Results Table.
E = (6.626 x 10-34 Joules•second) x (3.0 x 108 meters/second) your wavelength in meters for each metal
LAB REPORT REQUIREMENTS Claim, data table, calculations page (show conversion from nm to m) (show change E calculations), bar graph for wavelength AND bar graph for energy released (2 graphs) reasoning/conclusion
Sample data for
METAL COMPOUND COLOR OF FLAME
Calcium Chloride CaCl2 Red-Orange Blue green Copper Chloride CuCl2 red Lithium Chloride LiCl purple Potassium Chloride KCl red Strontium Chloride SrCl2 Yellow orange Sodium Chloride NaCl