Flame test
Introduction:
Just as a fingerprint is unique to each person, the color light emitted by metals heated in a flame is unique to each metal. When atoms of elements are heated or electrified, some give off visible colored light. For example, the familiar red glow of a neon sign is caused by neon atoms excited by electricity. Fireworks displays of bright lavender, red, green and yellow are the result of excited metal atoms. In fact, the kind of color given off by each atom is so exact that it can be used to identify that atom. You will test various metal salt solutions in a hot flame to learn the expected color given off by each excited atom.
Atoms have two kinds of states; a ground state and an excited state. The ground state is the state in which the electrons in the atom are in their lowest energy levels (orbitals) possible. Atoms naturally are in the ground state, so electrons need a source of energy to jump up to a higher energy level. In the ground state, electrons have the lowest possible values for “n” the principal quantum number.
Specific quantized amounts of energy are needed to excite an electron in an atom and produce an excited state. The excited electron is still “in” the atom even in an excited state. The valence electron will only escape the atom if the electron is given an amount of energy equal to the ionization energy for that atom.
When an element is burned, the electrons will be excited. Then as these electrons fall back from one energy level to another, they release energy and will emit photons of light. These photons will have different colors depending on the element and its discrete energy levels. That is, different wavelengths of light (colors) will be emitted when the electrons of different elements go down the step(s) between their energy level(s). Each element will have its own set of steps, therefore each will have its own color or set of colors.
Objective:
Small amounts of different salts are burned in the flame of a Bunsen burner. The characteristic color associated with each metallic ion will be observed and used to identify an unknown salt mixture.
Materials used:
Various elemental salts – 1g
Beaker
Bunsen Burner or Lamp Alcohol Burner
Water
Nichrome Wire or paper clip
8 little Beakers or Watch Glasses ( to contain 1 g)
| BaCl2 Barium Chloride | KCl Potassium Chloride |
| CaCl2 Calcium Chloride | NaCl Sodium Chloride |
| CuCl2 Copper (II) Chloride | SrCl2 Strontium Chloride |
| LiCl Lithium Chloride | Unknown mix |
Safety: Do not touch any of the solid chemicals
Process
1. Dip the nichrome wire (or paper clip) into the water and then hold it in the flame until red hot.
2. Dip the nichrome wire into the water again and then take the wire and scrape one of the element salts onto the wire. You will test only one salt at a time.
3. Place the wire into the Bunsen burner flame and observe.
4. Repeat steps 1-3 once again for other salts.
5. Record your observation onto your data table: Flame color
Results
Fill in the data table below.
Data Table:
| sample | Name of solid/ salt | Metal symbol | Color of Flame |
| A | Barium Chloride | yellow | |
| B | Calcium Chloride | Orange red | |
| C | Copper (II) Chloride | Blue green | |
| D | Lithium Chloride | Deep cherry red | |
| E | Potassium Chloride | Purple pink | |
| F | Sodium Chloride | Bright orange | |
| G | Strontium Chloride | Red orange | |
| H | Unknown | Blue green, yellow & red orange |
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