= Colligative property
A <colligative property> is a <solution (chemistry)> property whose dilute ideal limit depends on the number of dissolved particles relative to the <solvent>, rather than on their detailed identity. Examples include <freezing-point depression>, boiling-point elevation and <osmotic pressure>. Dissociation matters because one formula unit of dissolved <sodium chloride> can supply two <ions>.<Chemistry 2e by Paul Flowers and others>[Section 11.4, Colligative Properties and Colligative Properties of Electrolytes]{ref}
For dilute aqueous <chemical solutions>, the freezing-point change is approximately $\Delta T_f=iK_fm$, where $m$ is <molality>, $K_f$ depends on the <solvent>, and $i$ is the effective particle-number factor. Taking $K_f=1.86\,\mathrm{K\,kg\,mol^{-1}}$, $0.10\,\mathrm{mol\,kg^{-1}}$ <glucose> gives about $0.186\,\mathrm{K}$ depression, while ideally dissociated <sodium chloride> at the same <molality> gives about $0.372\,\mathrm{K}$. Interactions make real concentrated solutions depart from this ideal counting rule.<Chemistry 2e by Paul Flowers and others>[Section 11.4, freezing-point equation and experimentally reduced electrolyte factors]{ref}
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