Flame Lab | Logical Home Schooling

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Flame Lab Flame tests and emission spectra

About this activityChemistry · Physical Science · Grades 8–12 · About 50 minutes

Learning outcomes

Students will be able to:

Carry out flame tests, identify metal ions by flame color, and explain why the loop must be cleaned between tests.
Explain that atoms emit light when excited electrons drop to lower energy levels, and that bigger drops give shorter (bluer) wavelengths.
Use a spectroscope to see that each element has a unique line spectrum, and use spectra to tell apart elements with similar flame colors.
Identify unknown substances, the elements in a star, and the salts used in fireworks from their emission colors and spectra.

Standards alignment

HS-PS1-1 NGSS: Use the periodic table as a model to predict properties of elements based on patterns of electrons.
HS-PS4-1 NGSS: Use mathematical representations to support a claim about the relationships among frequency, wavelength, and speed of waves.
HS-ESS1-2 NGSS: Construct an explanation of the Big Bang theory based on astronomical evidence of light spectra (spectra connection).
SEP 3, 4 NGSS Science and Engineering Practices: plan and carry out investigations; analyze and interpret data.

Includes

Four stages: flame tests on seven metal salts plus a cobalt-glass challenge, a hydrogen energy-level model with an honors calculation, a spectroscope with element "barcodes," and identifying unknowns, a star, and fireworks; and a printable lab worksheet. A teacher answer key is available from Logical Home Schooling. See the whole electromagnetic spectrum in Spectrum Lab.

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Key ideas

Heat gives electrons energy, so they jump to higher energy levels.
When they fall back down, they give off that energy as light.
Bigger drop → more energy → shorter wavelength (violet/blue). Smaller drop → red.
Each element has its own set of levels, so its own line spectrum.

c = λν (c = 3.00 × 10⁸ m/s)
E = hν (h = 6.626 × 10⁻³⁴ J·s)
1 nm = 1 × 10⁻⁹ m

Flame colors and spectra are drawn to match real ones, simplified to the brightest lines.

Safety in a real lab

Goggles on, hair tied back, and never leave a burner unattended. The cleaning solution is dilute acid. Many of these salts are toxic, so wash your hands afterward.