Why Gallium Changes State So Easily
A metal’s melting point is the temperature at which its solid and liquid forms can coexist in balance. For gallium, that point is about 29.8°C (85.6°F)—close enough to ordinary indoor temperatures that a small change in heat can tip the balance. A hand at roughly 37°C transfers energy into the metal, allowing its orderly solid crystal to break down into a liquid.
The change is not instantaneous throughout a piece: heat must travel from the skin into the gallium, and melting itself takes energy. That is why a lump may first slump or develop a glossy wet-looking surface before becoming fully liquid.
The Unexpected Part: Liquid That Can Stay Liquid
Gallium can sometimes remain liquid even after it cools below its melting point. To freeze, its atoms must begin arranging themselves into a crystal; that process often needs a tiny solid seed or a suitable surface. Without one, liquid gallium can persist in a supercooled state—a liquid colder than the temperature at which it would normally freeze.
Once crystallization starts, the atoms settle into a solid structure and release heat, so the metal can seem to solidify suddenly. The contrast makes gallium a vivid demonstration that melting and freezing depend not only on temperature, but also on how readily a new crystal can get started.
