Neither. The condensation of oxygen gas is a phase change. The oxygen itself would be an element, not a mixture.
Oxygen is a chemical element not a mixture.
It is a homogenous mixture
Air is a homogenous mixture consisting to 78% of oxygen, 21% of nitrogen, and 1% of trace gases (the noble gases argon and xenon, for example.)
Clean air is a homogeneous mixture of nitrogen, argon, oxygen, water vapor and several other gasses present in small amounts. Air that is not "clean" is air that contains dirt and dust, etc, and is a heterogeneous mixture.
Oxygen is a chemical compound, not a mixture.
Oxygen is a chemical element not a mixture.
Neither, Oxygen is a pure substance not a mixture.
An element
Neither. Oxygen is an element, which is a pure substance and not a mixture.
It is a homogenous mixture
Smoke is heterogeneous mixture and is easily separable as it's main constituents are Carbon and Oxygen.
A heterogeneous mixture is a sum of pure substances which are not soluble in each other while a homogeneous mixture is a mixture wherein its constituents do not appear separately. Methanol is an example of a homogeneous mixture.
A smoke is solid particles dispersed in a gas, so it is heterogeneous.
It depends. You can have a gaseous mixture such as air, which would be a homogeneous mixture. But a single gas such as oxygen or methane would be a pure substance.
Water itself is an homogeneous mixture
All the elements are homogeneous so the oxygen is homogeneous, too.
Air is a homogenous mixture consisting to 78% of oxygen, 21% of nitrogen, and 1% of trace gases (the noble gases argon and xenon, for example.)