FLAME TEST LAB

What’s the lab about?

This lab was about identifying metallic ions using the colours they produce when heated in a flame. Different metals emit unique flame colours because of electron energy level changes.

How was the lab carried out? What did you do?

We lit a Bunsen burner and adjusted it to a blue non-luminous flame. Wooden splints soaked in known metal salt solutions were placed into the flame and the colours were recorded to create a flame test key. Then unknown solutions were tested and compared to the known flame colours to identify the unknown metallic ions.

What is the purpose of this lab?

The purpose was to identify unknown metal ions using flame tests and understand how electron transitions produce coloured light.

Can you identify/name the different pieces of equipment/materials that were used?

• Bunsen burner

• Flint striker

• Wooden splints

• Metal salt solutions

• Safety goggles

Can you identify which equipment would be best suited for each lab/goal?

• Bunsen burner → heating compounds

• Wooden splints → holding metal solutions safely

• Flint striker → safely lighting burner

• Goggles → eye protection

Do you know how to properly use the equipment?

The Bunsen burner must first be connected securely, lit with a striker, and adjusted to a blue flame by controlling airflow. Wooden splints are briefly placed into the hottest part of the flame. Goggles are worn at all times.

Can you explain the chemistry concepts demonstrated in this lab?

• Heating the chemicals provides energy to excite electrons in the metal ions.

• Electrons move from lower energy levels to higher energy levels when they absorb heat.

• As electrons return to their original (lower) energy levels, they release energy as light.

• The flame colour is produced by the light emitted during this energy release.

• Different metals produce different flame colours because each has unique energy level differences.

• The colour depends on the size of the energy gap between the excited and ground states.

• Heating is necessary because without added energy, electrons cannot become excited.

Can you discuss potential errors for the lab?

Possible errors:

• Flame not fully blue

• Contaminated splints

• Human colour perception differences

What can you identify about the unknown substances?

Metallic Ion	General Flame Test Colour
Li⁺	Crimson red
Na⁺	Bright yellow
K⁺	Lilac / light purple
Ca²⁺	Orange-red / brick red
Sr²⁺	Red / scarlet red
Cu²⁺	Blue-green / green