Chemistry / Unit 1 Chem 0039 short lesson, about 20 seconds
Compound
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The idea
A compound is a pure substance of two or more elements combined in a fixed ratio, separable only by chemical change.
In practice
Heating mercury(II) oxide breaks it into mercury and oxygen, revealing it was never a blend of loose ingredients.
Where people slip
A compound's properties differ completely from its elements — water is a stable liquid built from a flammable gas and one supporting combustion.
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