Q.Define

[!TLDR] Sublimation = solid-to-vapour directly, skipping liquid. Triple point = the unique T,P where solid, liquid and vapour all coexist. [!ANSWER] (i) Solid-to-vapour transition without passing th …

(i) SUBLIMATION (§7.8.1) is the change of state in which a substance passes directly from the SOLID state to the VAPOUR state (or vice versa) without ever passing through an intermediate liquid state; the substance is said to sublime. Dry ice (solid CO2) and iodine are classic examples -- both visibly shrink into vapour without ever forming a liquid puddle. During sublimation, the solid and vapour phases coexist together in thermal equilibrium. (ii) The TRIPLE POINT (§7.8.2) is the single, unique combination of temperature and pressure at which all THREE phases of a substance -- solid, liquid and vapour -- can coexist together simultaneously in equilibrium. For water, this occurs at exactly 273.16 K and $6.11\times10^{-3}$ atmosphere; this precise, reproducible po …

State both definitions precisely, and connect the triple point of water to its practic …

Confusing sublimation with ordinary evaporation (evaporation is liquid-to-vapour, sublimation is solid-to-vapour directly), or describing the triple point as merely 'where …