Thermal properties and temperature

$\Delta\theta$ in $E = mc\Delta\theta$ is final − initial, not the final temperature. Warming from 15 °C to 65 °C gives $\Delta\theta = 50$ °C, not 65 °C. Using the final temperature instead of the change is the single most common arithmetic error in this topic and loses the answer mark.

Evaporation happens at the surface, at any temperature and cools the liquid (the fastest molecules escape, lowering average KE). Boiling happens throughout the liquid, only at the boiling point. Condensation is the reverse of evaporation (gas → liquid) — a common MCQ mix-up. (E) Evaporation rate rises with surface area, temperature and air flow.

A specific heat capacity definition needs two elements: energy per kilogram AND per degree (1 °C). Zero-scoring forms: "energy to heat a substance by 1 °C" (no per-kg); "energy per kilogram" (no temperature); "heat capacity" (that is J/°C). (E) For latent heat, never say it "causes a temperature change" — temperature stays constant.

At the melting/boiling point the temperature stays constant while energy is still supplied — the most-tested misconception here. The energy breaks intermolecular bonds, not particle KE, so temperature (average KE) does not rise. On a heating curve, slopes = temperature rising, plateaux = change of state. "Temperature increases during melting" scores zero.

(E) Specific heat capacity ($c$, J/(kg °C)) applies when temperature changes within one state — $E = mc\Delta\theta$. Specific latent heat ($L$, J/kg) applies during a change of state at constant temperature — $E = mL$. On a heating curve, sloped sections use $c$ and flat plateaux use $L$.