Problem — Planet without latent heat

Problem

On an imaginary world, water passes from solid to liquid to vapour without spending latent heat: the transition is instantaneous, and all the heat supplied always goes into a temperature increase $\Delta T$. What would change in everyday life? Discuss in five lines, considering ice in tea, sweating, climate and the oceans.

Solution

Without latent heat, the “thermal flywheel” of phase transitions would disappear, i.e. that enormous quantity of energy that today is absorbed or released at constant temperature during melting and evaporation. Ice in tea: it would melt and heat up instantaneously, cooling the drink very little, because it would no longer draw off the roughly $334 \ \text{J/g}$ of latent heat of fusion. Sweating: it would be completely ineffective, because evaporation would no longer carry away the roughly $2260 \ \text{J/g}$ of latent heat and the body would fail to cool down. Climate: without the accumulation and release of energy in melting and evaporation, there would be violent temperature swings, storms and unstable seasons, with no damping whatsoever. Oceans: the moderation due to the continuous cycles of evaporation and condensation would be lost, and bodies of water would no longer stabilise coastal temperatures. Latent heat is a huge thermal stabiliser: without it, the planet’s climate and biology would be radically more unstable (Bloomfield 2016) Riferimenti bibliografici.

Collegamenti

Argomenti: Termologia Concetti: Calore latente e cambiamenti di stato