I just started my study of thermodynamics. I am having problem in uderstanding a concept.

Suppose I drop an ice-cube and a rock of cube shape. Which one will reach the ground first? I know ratio of Work to Heat equals Joules Constant. Therefore any change in potential energy will result in heat which in return will melt ice cube thus mass is changing. Will internal energy of ice cube change till it reaches the ground? If mass of ice cube is changing what will be the ratio of kinectic energy of ice cube to that of rock.