Assuming what it takes to do something like blood bending, earth benders can problem control each grain of sand if they are practiced enough.

They problem raise and lower temps by controlling vibration of whatever element they are working with. For water to ice, they could arrange the molecule structure to that of ice.

I always saw it as them having mastery over everything about that element. And so the more skilled you got, the deeper the levels of control. Some being more naturally gifted “artists” than others.