Are colloids heterogenous mixtures or homogenous mixtures?
A heterogeneous mixture is one in which the two phases (the dispersed phase and the continuous) are either of different states (e.g. solid in liquid), or if they are of the same state, one is not soluble in the other (e.g. oil in water). For these reasons colloids are generally considered to be heterogeneous mixtures in the chemical sense, although some may still regard them as homogeneous in the physical sense (i.e. the properties are uniform as one moves through the material, rather than being, for example, very high viscosity at the bottom of the container, and lower viscosity at the top).
But from a chemical perspective, colloids are regarded as heterogeneous mixtures (as opposed to things such as solutions - for example, a solution of copper sulphate in water - which are of 1 single phase, and therefore would be chemically homogeneous).