The correct answer according to the uniformity the difference is whether you can distinguish more than one part in the mixture.
Explanation:
A homogeneous mixture is one in which with the naked eye or with a microscope no different parts can be distinguished. Its composition and properties are the same at all points, the substance is uniform.
In a heterogeneous mixture, we can observe different parts. Its composition is variable. It can be broken down into simpler substances by physical processes. The substance, in this case, is not uniform.
Evaporation can decrease the amount of water. Dust from the surroundings can enter the water. The water can freeze if the surrounding temperature decreases sufficiently.
