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?

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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?

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Answer 1 · 2016-01-18T20:42:22

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Explanation:

The question describes an experiment similar to the decomposition of copper(II) carbonate ( $C u C O_{3}$ $CuCO_3$ ) which is when heated in decomposes into carbon dioxide gas ( $C O_{2}$ $CO_2$ ) and copper(II) oxide ( $C u O$ $CuO$ ) according to the following decomposition reaction:

$C u C O_{3} (g) \to C O_{2} (g) + C u O (s)$ $color(green)(CuCO_3(g))->color(gray)(CO_2(g))+CuO(s)$

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
Odor
Color change
etc.

Here is a video on physical and chemical change that describes the aforementioned experiment:

Lab Experiment #2: Physical & Chemical Changes.

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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?

1 Answer

Explanation:

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