Does Shape Affect How Fast an Ice Cube Will Melt?

Shape can drastically alter the amount of time it takes for an ice cube to melt. Given standard atmospheric pressure, ice cubes melt when their temperature rises above 32 degrees Fahrenheit. This only happens if the ice cube absorbs heat from its environment. The greater the ice cube’s surface-to-volume ratio is, the faster it melts.

Ice cubes have a moderate amount of surface area, relative to the volume they contain. For instance, 1 cubic inch of water has 6 square inches of surface area. If the same amount of water were frozen into the shape of a sphere, the surface area would be less than 5 square inches of surface area. This means that in order to keep a given volume of ice from melting, spheres work better than cubes do. Conversely, if the ice cube is formed into a 2-inch-by-2-inch square, a mere one-quarter inch thick, its surface area grows to 10 square inches.

This phenomenon is reflected in the real world. When the ice begins melting after a winter storm, the first ice to melt is that which has the highest surface area. This is usually the thin ice that covers the roads and trees. Puddles, on the other hand, take much longer to melt.