On youtube, a bunch of Rayleigh scattering experiments (e.g this one are set up with some compound being added to water in order to invoke the effect.
Why is there no Rayleigh effect for "pure" water? In other words, why is there no visible scattering effect before the compound is added?
Is it because in its liquid state, there are no separate "particles" floating around? If so, why does this matter?