When you heat a solid, you expect it to melt and when you boil water, you can be pretty certain that it will turn into vapour. But what about a liquid that becomes solid when it's heated? Of course, it has already been done, for example in the chemical process of polymerization.
A slurry of any powder of grains like wheat, rice or maize changes into a solid mass on heating. Here, the change is chemical and irreversible, meaning you cannot get the slurry back on cooling the solid.
In recent years, a team of French physicists has discovered that a solution of compounds, namely α-cyclodextrine (αCD), water and 4-methylpyridine (4MP), when heated between 45° and 75°C, solidifies. But the process is fully reversible and on decreasing the temperature, this solid melts and reverts to a liquid.
Studies have revealed that the solid phase is a “sol-gel” system in which the water sticking to the αCD and 4MP leads to a liquid phase at lower temperatures. At higher temperatures, however, the water molecules leave the αCD, which results in the solution solidifying.
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