What causes freezing point depression on a molecular level?

Question

Mateo Aguilar · Accepted Answer

On the particle level...........?

The simplest answer is #"solute-solvent"# interaction. Especially when an ionic salt dissolves in aqueous solution, the individual ions are solvated by water molecules...... #NaCl(s)stackrel("water")rarrNa^+(aq) + Cl^(-)(aq)# The individual sodium and chloride are present as their #"aquated ions"#, which is what we mean by #"(aq)"#, probably we deal with #[Na(OH_2)_6]^+# as the dissolved species; and these solute/solvent interactions cause measurable changes to the bulk properties of the solution: i.e. #"boiling point elevation"#; #"freezing point depression"#; #"changes in osmotic pressure"#. The observed change in these properties is proportional to the number of particles in solution, i.e. the concentration of the solute particles. If we had equimolar sodium chloride and calcium chloride, how would these so-called colligative properties compare?

Natalie Anton · Answer

undefined Freezing point depression occurs when solute particles disrupt the formation of the orderly arrangement of solvent particles in a solid state, lowering the freezing point of the solution compared to the pure solvent. This disruption arises from the solute particles occupying spaces between solvent particles, thereby making it more difficult for the solvent particles to organize into a solid structure.