When you get a cup of hot coffee and a glass of cold beer, what should you drink first? Does the coffee get cooler faster than the beer warms up? Based on our everyday experience, one would expect that the answer depends only on how much the temperature of the two drinks differs from their ambient temperature. If the difference is the same, both processes should occur at the same rate. This does not apply on the nanoscale though: Small systems warm up faster than they cool down. The Göttingen Max Planck researchers Aljaz Godec and Allesio Lapolla have now mathematically proven this.
When thermodynamic equilibrium is restored after a rapid change in temperature – in this example, the temperature of beer or coffee – the so-called free energy is the driving force. It is composed of two driving forces that work against each other: entropy and potential energy.
“When we tap a cold beer, its ambient temperature changes because it is much cooler in the barrel,” explains Lapolla, a PhD student in Godec's research group at the Max…