Any liquid is made up of a large number of molecules. These molecules attract each other, so you can think of them as a collection of sticky particles. When the temperature is low, the particles don’t move around as much, and since they are sticky they get trapped in a single arrangement and don’t move at all. This is the transition from liquid to solid. So, when water molecules in liquid water become cold enough, the attractive bonds between the molecules become strong enough to lock the molecules into a solid crystal: ice.

To melt an ice cube, you reverse this process. By adding heat energy, you force the water molecules in ice to become unstuck, allowing them to move around as a liquid again. The time it takes to melt the ice depends on how quickly you can add heat. The best way to determine this time is to measure it yourself.

Two big things that affect how quickly you can add heat are the surrounding temperature, and the surface area of the ice. You can test both of these things to see which has a greater effect on melting! You will need a watch or stopwatch to keep the time, ice cubes, and a bowl for water. To test the impact of temperature, record how long an ice cube takes to melt in hot, warm, and cold water (the easiest way to do this is with water from the sink, or you could boil water to make it really hot). To test the impact of surface area, compare how long it takes for a whole ice cube to melt in water with the time it takes for a crushed ice cube to melt in water. A lot of small pieces of ice will have much more surface area than one big piece of ice. Can you guess which will melt faster?