I first explain what thermal equilibrium is. Thermal equilibrium is very simple a situation where an object has got the same temperature as the environment.
The temperature of a substance is and measure for the energy with which the particles move in that substance.For example, if an object has a higher temperature than the environment, the particles will move on average more energy than the particles in the environment. If collisions between the particles of the object and the environment can occur, energy will be exchanged for those collisions. With a calculation you can prove that the particles that move with more energy return energy and the particles that move with less energy get energy (the total amount of energy remains the same).
This practically means that the temperature of the object decreases (the particles have less energy) and that the temperature of the environment rises (but that is usually so big that you don’t or barely notice that).This process continues until the particles of the object move as much energy as the particles in the environment. NET no more energy is exchanged and we have reached a state of thermal equilibrium. This also means that the object and its environment have the same temperature.
Thermodynamic equilibrium is a situation in which not only the temperature (thermal) is in equilibrium, thus the kinetic energy of the particles, but also the forces on the particles e.g.Due to pressure differences (mechanically). Sometimes a chemical potential is also counted here, especially by chemists.
Therefore, it does not ensure that a substance can reach a temperature above its melting point without changing its condition.A concrete example: if I put an ice cube in a large bowl of water at room temperature, the ice cube will warm up until it has the same temperature as the water in the container and thus melt. The water in the bucket will drop slightly in temperature, but because the bucket contains much more water than an ice cube it will not be measurable.
It has nothing to do with the material properties.
It means that there are different forces that work opposite and are about the same size.
An example of this is our sun.Gravity tries to push the sun together. The heat produced by Fusion tries to push the sun apart. These two forces keep each other in equilibrium, which makes the sun’s size and temperature reasonably constant.
In addition to Maarten his answer, because I saw no answer for the second question.
Yes, this can lead to temperatures of substances where the melting point is exceeded.Or boiling point.
Cold welding for example.
Or if your water is going to boil, the heat source (e.g.Fire) takes care of the boiling point for evaporation and the evaporation ensures thermodynamic equilibrium in the water. This will keep the same pressure and temperature (100 掳C).