AQA GCSE FOUNDATION Chemistry: Flame Tests

Flame Tests: Identifying Metal Ions

Flame tests are a simple and effective way to identify the presence of certain metal ions in a sample. When a metal ion is heated in a flame, the electrons in the metal atom absorb energy and jump to higher energy levels. When these excited electrons return to their ground state, they release energy in the form of light. The color of the light emitted is characteristic of the specific metal ion.

Materials:

• Bunsen burner
• Safety goggles
• Wire loop (usually made of nichrome wire)
• Sample of unknown metal salts
• Dilute hydrochloric acid (HCl)
• Distilled water

Procedure:

1. Safety First: Always wear safety goggles to protect your eyes from any potential splashes or flames.
2. Clean the Wire Loop: Dip the wire loop into dilute hydrochloric acid and then hold it in the Bunsen burner flame until it glows brightly. This removes any contaminants from the wire.
3. Obtain Sample: Dip the cleaned wire loop into a small amount of the unknown metal salt.
4. Hold in Flame: Hold the loop in the Bunsen burner flame, preferably in the hottest part of the flame (the roaring blue inner cone).
5. Observe Flame Color: Carefully observe the color of the flame. The color of the flame will indicate the presence of a specific metal ion.

Common Flame Test Colors:

Important Notes:

• The flame color observed may be influenced by the presence of other metal ions in the sample.
• Some metal ions may not produce a distinct flame color.
• It is essential to clean the wire loop thoroughly between each test to avoid contamination.
• Always dispose of chemicals responsibly.

Example:

If you observe a bright yellow flame, it is highly likely that the sample contains sodium ions (Na+).

Flame Tests: A Valuable Tool

Flame tests provide a quick and easy way to identify certain metal ions in a sample. This technique is valuable in various fields, including chemistry, environmental science, and forensics.