International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

What is the correct procedure for performing a flame test?

1. Add liquid to a test tube and heat it

2. Put solid onto a wire and place it in a blue flame

3. Mix the substance with water then heat

4. Burn the solid directly in the flame without a wire

The correct answer is: Put solid onto a wire and place it in a blue flame

The correct procedure for performing a flame test involves placing a solid sample onto a wire, usually made of a material like platinum or nichrome, and then introducing it into a flame, typically a blue flame from a Bunsen burner. This method effectively allows for the observation of the characteristic colors emitted by different metal ions when they are heated, aiding in the identification of the substance being tested. During the flame test, the heat from the flame excites the electrons in the metal ions, causing them to jump to higher energy levels. When these electrons return to their ground state, they release energy in the form of light, which is seen as specific colors. Each metal ion produces a distinct flame color, making it a valuable qualitative analysis tool in chemistry. The other procedures mentioned involve methods that are not suitable for flame tests. Adding liquid to a test tube and heating it doesn't allow for the observation of flame colors associated with metal ions. Mixing the substance with water before heating does not help in identifying flame color. Burning the solid directly without the aid of a wire may not facilitate the same level of control and could produce inconsistent results, making it less effective for this specific identification method.