Boiling-Point Elevation

A non-volatile solute lowers the solvent's vapor pressure, so the solution must be heated a little hotter before that pressure reaches the atmosphere's — the boiling point rises. The rise depends only on how many particles are dissolved, not what they are, scaled by the solvent's ebullioscopic constant K_b. Water's K_b is a modest 0.512 K·kg/mol: a hearty 1.0 mol/kg sugar solution boils at just 100.5 °C, which is why salting pasta water changes its flavor far more than its physics.

Other solvents respond much more strongly — benzene's K_b is 2.53 and camphor's freezing-side cousin is famously huge — and remember that ionic solutes count each ion: 1 mol/kg NaCl acts as nearly 2 mol/kg of particles. Solved backwards, a measured ΔT_b divided by K_b gives the molality, the classical route to a dissolved compound's molar mass before mass spectrometers existed.