two or more pure substances combined that retain their unique properties. Mixtures include homogeneous mixtures, also called or solutions, where one can not distinguish the different parts, and heterogeneous mixtures, in which you can distinguish the different parts. Mixtures are physically combined and can be physically separated. For example, rainwater is a homogeneous mixture as the particles of gas dissolved in them are evenly distributed and cannot be seen. River water is commonly a heterogeneous mixture where you can see soil particles or sediments floating in the water.