Here is a ¥1-coin made of aluminum (Al) floating on the surface of dihydrogen monoxide (H2O). The density of aluminum (Al) is about 2.7 Mg/m^3, which is greater than 1.0 Mg/m^3, the density of dihydrogen monoxide (H2O). The coin floats on water due to the surface tension.
As soon as a drio of detergent is introduced, the coin sinks because the detergent contains surfactants which are surface-active agents that reduce the surface tension.
