Elaborate how the atmosphere could be considered as both a homogenous and heterogeneous mixture.

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ncchemist | eNotes Employee

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You are only allowed to ask one question at a time so I edited down accordingly.  Since the Earth (and as a result its atmosphere) occupies so much volume, it depends on whether you consider it as a whole or in small parts as to whether it is a homogeneous or heterogeneous mixture.  If you consider the atmosphere of the planet as a whole, all of the major gasses (nitrogen, oxygen, and the other trace gasses) are essentially totally mixed up evenly to make a homogeneous mixture.  There are no "pockets" of oxygen or any particular gas located anywhere.  But on a smaller scale there are concentrated locations of water vapor in the form of clouds.  These clouds are clearly visible as a separate phase from the rest of the atmosphere, thus leading to a heterogeneous mixture.  So both descriptions could be applicable.