Final answer:
Ice melts when the cohesive bonds between water molecules are broken. This requires an input of energy, typically in the form of heat from the surroundings. The temperature of ice remains constant until all of it has melted.
Step-by-step explanation:
The forces that must be overcome for ice to melt are cohesive bonds between the molecules in the solid. When ice melts, the cohesive bonds between the water molecules need to be broken so that the water molecules can move around freely. This requires an input of energy, which is typically heat from its surroundings. As a result, the ice transitions from a solid to a liquid phase without a change in temperature.