The water molecules in ice are more strongly attached to each other than they are when the ice is melted. That is why ice is a solid. As the ice warms up, the heat makes the molecules move around more and more. When it is warm enough, the molecules cannot stay stuck to each other like they did when they were ice. It is when they break away from each other that melting happens. If you continue to heat the water that came from the ice, it will warm until it boils. When that happens, the molecules cannot hold on to each other at all. When they break away, they boil off as an invisible vapor. When that vapor cools a little it makes the fog we call steam. Water has a melting point of 32* degrees Fahrenheit (0* degrees Celsius). This means that water melts at about that temperature. If the temperature starts to warm above this, the ice melts. Ice always melts around the outside, where it is covered with water. Heat is just fast, hard shaking of the little molecules stuff is made of. In a block of ice, all the water molecules are glued together in a fixed pile. When one adds heat to the outside of ice, the water molecules start falling off the outside of the pile, one layer at a time. Once they fall off, they swim around sticking together like mud. That's the wet, liquid water that the ice turned into, when it melted. When the molecules come free, they use up some of the shaking. Using up heat by melting keeps the rest of the ice cold. The ice stays cold inside even while the room around it is warm. So the rest of the ice sits there, cold, waiting for some more heat to drift over to it. When some heat comes near, the ice eats it up and melts a little more. And the part that remains is still cold. It can take a long time for a large piece of ice to find enough heat to melt completely.