A light green powder is heated in a test tube. A gas is given off, and the solid becomes black. Was the change physical or chemical, and is the green powder an element, a compound, or a mixture?
The question describes an experiment similar to the decomposition of copper(II) carbonate (
Therefore, the green substance is a compound and the change is a chemical change since giving off a gas is one of the several indication of a chemical change that include:
- Gas evolution
- Formation of a precipitate
- Evolution of heat
- Color change
Here is a video on physical and chemical change that describes the aforementioned experiment:
Lab Experiment #2: Physical & Chemical Changes.