According to an article from Physics Today, ice is slippery because there is a “liquid or liquid-like layer” on its surface.
There are 3 mechanisms that can cause this layer to exist, each playing a role that depends on the temperature, and other factors. These mechanisms are:
- Pressure melting (the least dominant)
- Frictional heating
Pressure melting and frictional heating can cause a liquid water film to form on top of the ice, while premelting can cause a liquid-like layer to form.
Premelting refers to the formation of quasi-liquid layers (QLLs) on the surface of a solid crystal even below its melting point. This quasi-liquid layer forms because molecules on the surface are bonded to fewer other molecules when compared to molecules which are below the surface. Therefore, molecules on the surface are less firmly held in place and can move around more.
If premelting occurs when molecules on the surface of a crystal move around because they are bonded to relatively fewer other molecules, does this happen with other crystals such as sugar at room temperature?
Just like water molecules in ice, sucrose molecules are held in place in a sugar crystal via hydrogen bonds. So premelting at room temperature might be possible, perhaps with the quasi-liquid film having a lower thickness in the case of sugar.
On the other hand, according to this paper, the melting point of sucrose is 185 °C. Perhaps this is too high for premelting to occur at all at room temperature?