Explanation:
A pure substance is a substance that consists one or more atoms present in similar composition.
For example, aluminium, carbon dioxide, magnesium sulfate etc are all pure substances.
Whereas mixtures are the substances that contains two or more atoms mixed together in a different composition.
When molecules of solute are evenly distributed into the solvent then it is known as a homogeneous mixture.
For example, NaCl in water, sweat, sugar solution etc are all homogeneous mixtures.
When molecules of a solute are non-uniformly distributed then it is known as a heterogeneous mixture.
For example, sand in water, vegetable soup etc are heterogeneous mixtures.
Thus, we can classify the given substances as follows.
a) Sweat - homogeneous mixture
b) Carbon dioxide - pure substance
c) Aluminium - pure substance
d) vegetable soup - heterogeneous mixture
