There Is None
Solids
There are very few solids that cannot be melted because melting is a physical process that most solids can undergo. However, some examples of solids that are considered to be "non-melting" are diamond (composed of carbon atoms held together by strong covalent bonds) and some ceramics (like boron nitride) that have very high melting points.
In solids, the type of energy that cannot take place is translational kinetic energy. This is because the particles in a solid are closely packed and held in fixed positions, allowing only vibrational motion around their equilibrium positions. As a result, solids do not allow for free movement of particles that would be necessary for translational motion, which is more characteristic of liquids and gases.
A gas cannot go through non-porous solids.
No, ionic solids typically do not have high conductivity when solid because the ions are held in fixed positions and cannot move freely to carry an electric current. Conductivity in ionic solids usually occurs only when they are molten or dissolved in a liquid, where the ions are free to move.
A crystalline solid held together by covalent bonds
Solids do not mix together because their particles are held tightly in place by strong intermolecular forces. When two solids are placed on top of each other, these intermolecular forces prevent the particles from moving and intermingling with each other, thus maintaining their individual structures.
insoluble
solid particles cannot move.
solids
Solids have a strict shape and volume. Solids do not flow and they are usually cannot be easily compressed.
The forces holding the atoms together are weaker in liquids than in solids -Apex