Colligative Properties & Osmosis

A U-tube separated by a semipermeable membrane: solvent flows into the solution and the column rises until its extra pressure — the osmotic pressure π = i·c·R·T — stops the net flow. Students vary concentration and temperature and switch the solute between glucose (i = 1), NaCl (i = 2) and CaCl₂ (i = 3), watching π, the boiling-point elevation and the freezing-point depression all scale with the number of dissolved particles. It makes the central idea concrete: colligative properties count particles, not identity — so the van't Hoff factor is what really drives them.