Ice cubes are added to a glass of pure water and a glass of pure alcohol. The ice would be

Density of water is approx 1g/ml; Density of Ice is approx 0.93g/ml; and Density of 100% pure ethanol is 0.79g/ml. So the density of ice cubes is lesser than water, but higher than alcohol. So it will float in water, but sink in alcohol. This can also be put as: The ice cube will float higher in water as compared to alcohol.