Bipolarity

I have seen in my textbook that most colligative properties are defined in terms of molality. This must mean that there is some relation between molality and the von Hoff factor, since von Hoff factor is directly related to the colligative properties.

However, as far as I know, the only difference between molarity and molality is that molarity is measured in terms of volume of solution, whereas molality is measured in terms of kilograms of solvent.

So where does the von Hoff factor come in when defining molality? If it doesn't play a role in defining molality, then my book could have used molarity without being incorrect?

Thanks.

BiP