Thermal Decomposition of Copper Carbonate

Materials: ★★☆ Available in most school laboratories or specialist stores
Difficulty: ★★☆ Can be done by science teachers
Safety: ★★☆ Some safety precautions required to perform safely

Categories: Chemical Reactions, Colour Changes, Compounds

Alternative titles: Heating Copper Carbonate

Summary

When copper carbonate is heated, it thermally decomposes to form copper oxide and carbon dioxide. The reaction is accompanied by a visible color change from green to black, and the gas produced can be confirmed as carbon dioxide by bubbling it through limewater, which turns cloudy.

Procedure

Place a small amount of copper carbonate powder in a clean, dry test tube.
Secure the test tube in a clamp stand and gently heat it with a Bunsen burner.
Observe the color change from green to black as the copper carbonate decomposes to form copper oxide.
To test for carbon dioxide, connect the test tube with delivery tubing to another test tube containing limewater.
Continue heating and observe that the limewater turns cloudy, confirming the presence of carbon dioxide.

Links

Copper carbonate over a flame - Mr E's Science Episodes:

Thermal Decomposition of Copper(II) Carbonate - Curly Arrow Chemistry:

Variations

Repeat the experiment with other metal carbonates such as zinc carbonate or calcium carbonate to compare their ease of decomposition.

Safety Precautions

Wear safety goggles and a lab coat to protect from splashes or hot materials.
Use tongs or a clamp to hold the test tube; do not touch it during or immediately after heating.
Ensure good ventilation or work in a fume hood to avoid inhaling any gases.
Allow the apparatus to cool before handling.
If bubbling into limewater, then remove tube from limewater before removing heat in order to prevent water being sucked into the hot test tube and forming steam.

Questions to Consider

What type of reaction is this? (It is a thermal decomposition reaction.)
How can you tell that a chemical change has occurred? (A color change and gas production are observed.)
What are the products of heating copper carbonate? (Copper oxide and carbon dioxide.)
Why does limewater turn cloudy when carbon dioxide is passed through it? (Because calcium carbonate forms as a precipitate.)
Do all metal carbonates decompose at the same temperature? (No, more reactive metals form more stable carbonates that decompose at higher temperatures.)