Summer STEM Challenge – Ice Melting Race

Ice melts when it absorbs heat energy from its surroundings, causing its molecules to move faster and break out of their frozen structure into liquid water. This experiment tests how different conditions affect the rate of that heat transfer.

Direct sunlight wins because the sun delivers a continuous, powerful source of heat energy — far more than room temperature air alone. Aluminum foil comes in second because it's an excellent heat conductor, meaning it absorbs warmth from the surrounding air and transfers it efficiently to the ice cube inside. The control cup melts slowly because the only heat source is the ambient room temperature air, which delivers energy at a much slower rate. Salt is the wildcard: it initially lowers the freezing point of water, causing a quick melt wherever it makes contact. But as the ice begins to liquefy, the ice cube ends up sitting in very cold, salty water that actually insulates it and slows the rest of the melting down.

This principle is exactly why salt is spread on icy roads in winter — it disrupts the freezing point and helps break down ice quickly. The same science also explains why foil-lined coolers keep food cold longer, and why your icy drink stays cold differently depending on what's around it.