Colligative

the water cannot tell sugar from salt. it can only count.

drop crystals into the water and watch both the boiling and freezing point move -- identity never enters the formula, only the count of particles does

Dissolve something in water and both its boiling point and its freezing point shift -- but by how much depends only on how many separate particles end up in solution, never on what those particles are. A sugar molecule stays one particle when it dissolves; a formula unit of table salt splits into two ions, and calcium chloride into three, so the same one mole of solute pushes the shift two or three times as far. That is why we salt icy roads with something that dissociates rather than sugar, and why antifreeze works at all -- the water genuinely cannot tell the solutes apart, it can only count what is floating in it.

Concepts: chemistry, phase-change.

An interactive you play with one thumb, on Wundr.