Do Not Wear Gloves: Do not wear gloves for this experiment. Although gloves are sometimes useful to protect against chemicals, they can melt to your skin if heated above their melting point.
Wear Goggles at All Times: Wear goggles to protect your eyes from the chemicals used in this experiment.
Be Careful of Open Flames: Always be careful around open flames. Do not wear loose clothing that might come in contact with the flame, and be sure to tie back long hair.
When energy is added to an atom in the form of light, heat, or electricity, the electrons absorb this energy and, as a result, move to higher energy levels called excited states. However, because it is more stable for electrons to have lower potential energies whenever possible, they eventually return to their original orbitals.
When electrons fall back toward the nucleus, energy is released from the atom as light. Depending on the distance the electron falls, and the amount of energy given off, a specific color of light is emitted. We can use the color of the light emitted by an element to determine the different locations of its electron orbitals. The differences in orbital location and potential energy values are unique for every element. This means that each element gives off a unique color, based on the combination of the wavelengths of light it produces.
It is common in science to take an unknown element or compound, discovered in nature or created in a reaction, and compare its properties to different known substances to see if it can be identified. The flame test is one way that scientists can identify the elements present in a given sample.
In this part of the lab, you will be conducting a flame test. First, you will observe each of the given elements in the flame of the Bunsen burner. Be sure to record your observations carefully. Next, you will be given two unknown elements that you will identify by comparing their flame color to the known elements you observed.
| Known Elements | Color |
|---|---|
| Barium | Green |
| Calcium | Red |
| Sodium | Yellow |
| Rubidium | Violet/Blue |
| Potassium | Blue |
| Lithium | Magenta |
Follow the same steps as above to test two unknown solutions and observe their color in the Bunsen burner flame.
| Unknown Elements | Color |
|---|---|
| Unknown One | Yellow |
| Unknown Two | Blue |
Review your data and use the known elements to identify the unknowns, unknown one and unknown two.
Spectroscopy is the analysis of line spectra and of the way in which light interacts with matter. To analyze the line spectrum of a given light source, the light passes through a narrow slit in order to produce a beam of light. That beam of light is then separated using a prism or grating. The different colors of visible light appear as lines in the line spectrum because the prism separates the light waves by their wavelength.
Different elements produce different line spectra because each type of element has unique spacing between its energy levels. The different line spectra of the elements are unique enough to be used to identify elements. In this lab, you will use a spectroscope to observe the line spectra of the given elements. Be sure to record observations in your data table because you will be using these observations to help you identify unknown elements.
| Spectrum Line | Hydrogen | Helium | Sodium | Neon | Mercury |
|---|---|---|---|---|---|
| 1 | Violet/blue, 410 nm | Blue, 445 nm | Dark yellow, 580 nm | Violet/blue, 420 nm | Blue/violet, 430 nm |
| 2 | Blue, 440 nm | Green, 510 nm | Dark yellow, 585 nm | Green, 515 nm | Blue, 450 nm |
| 3 | Green, 510 nm | Dark yellow, 585 nm | Yellow/Orange, 595 nm | Green, 520 nm | Green, 540 nm |
| 4 | Green/yellow, 535 nm | Red, 690 nm | Green, 525 nm | Green/yellow, 550 nm | |
| 5 | Yellow, 550 nm | Dark red, 735 nm | Yellow, 575 nm | Yellow, 570 nm | |
| 6 | Dark yellow, 570 nm | Dark yellow, 580 nm | Red, 675 nm | ||
| 7 | Red, 660 nm | Red, 700 nm | Red, 690 nm | ||
| 8 | Dark red, 680 nm | Dark red, 710 nm | Dark red, 710 nm | ||
| 9 | Dark red, 700 nm | Dark red, 720 nm | |||
| 10 | Dark red, 745 nm |
Observe the line spectrum of the star, which has 18 total lines in its spectrum. Because there are so many lines present, you can record the color and wavelength of the brightest/thickest lines (shown as bold below) in the spectrum.
| Line in Star Spectrum |
Color | Wavelength |
|---|---|---|
| 1 | Violet | 405 nm |
| 2 | Violet | 410 nm |
| 3 | Violet/Blue | 420 nm |
| 4 | Blue | 440 nm |
| 5 | Blue | 445 nm |
| 6 | Green | 500 nm |
| 7 | Green | 505 nm |
| 7 | Green/Yellow | 550 nm |
| 8 | Green/Yellow | 560 nm |
| 9 | Yellow | 580 nm |
| 10 | Orange | 620 nm |
| 11 | Orange | 630 nm |
| 12 | Red | 650 nm |
| 13 | Red | 680 nm |
| 14 | Red | 690 nm |
| 15 | Red | 700 nm |
| 16 | Dark red | 710 nm |
| 17 | Dark red | 715 nm |
| 18 | Dark red | 725 nm |
Congratulations! You have successfully completed the spectroscopy lab. Use the data you’ve collected in the data table to help you hypothesize which elements might be found in the star’s spectrum.