1 of 9 images in a sequence showing chemical waves in a Belousov-Zhabotinsky (BZ) reagent. This is a well-mixed solution of citric acid, potassium bromate and a cerium sulphate catalyst. If the local relative concentrations in the reagent are altered, for example by the impact of a dust particle on the surface, the equilibrium of the reaction is disturbed. The reaction then oscillates between oxidation and reduction. The oscillation propagates through the solution as a concentration front (yellow lines), caused by the dynamic coupling between the propagation rate of the reaction and the rates of diffusion of the reagents. Such chemical waves may be modeled using chaos mathematics.