The Belousov-Zhabotinsky (BZ) reaction is a chemical clock: in a shallow
PHYSICS · Multi-part · Fermi University Physics · Thermal, Statistical & Complex Systems · Non-equilibrium statistical mechanics and stochastic thermodynamics · Complex and collective systems
Many Parts, One Behaviour, Ch Emergence and self-organisation: collective order from local rules
Problem
The Belousov-Zhabotinsky (BZ) reaction is a chemical clock: in a shallow, sealed Petri dish a uniform, colourless mixture of reactants turns spontaneously into rotating spiral bands of blue and red that persist for tens of minutes before fading.Someone argues: "The mixture began with no visible structure and ended with a clear spatial pattern, so its entropy must have decreased. Since the entropy of an isolated system cannot decrease, the BZ reaction breaks the second law of thermodynamics."
((a)) Identify the step in this argument that is wrong.
((b)) State what happens to the spiral pattern once the reactants in the sealed dish are used up, and say what this shows about the kind of order the BZ reaction produces.