Melting Ice

why does ice melt faster in water than in air?
- mt

Good question! When ice melts, it changes from a solid (ice) to a liquid (water). In order to make something change from a solid to a liquid, you have to heat it up. That’s because when you heat something up, you give it more energy, which makes the molecules (the tiny little things that make up stuff) move faster and faster. When the molecules move faster, they have a harder time holding on to each other, so the stuff becomes less solid and more liquid. (If you were to heat it up even more, it would become a gas.) So to melt the ice, you have to add heat.

So then the question becomes, if the air and the water are the same temperature, why does the water heat up the ice cube more than the air does? The reason for that is that water is a better "conductor" for heat-energy than air is. What that means is that the heat can travel through the water to reach the ice more easily than it can go through the air.

(Heat can actually move through water more than 20 times as quickly as it can move through air! The reason that the ice in water doesn’t melt 20 times faster than the ice in the air does is because the ice in the air is probably sitting on something - like a glass plate, and glass is an even better conductor than water is. And metal conducts heat even better than that!)

-Tamara

(published on 10/22/2007)