It is a well-known fact that a substance can be in one of the states - gaseous, liquid, solid. And it can move from one to another. The simplest example is a piece of ice melts, turns into a liquid and then into steam. In this whole process of converting a solid into steam, the melting stage is very interesting and one of its parameters is the specific heat of melting.
Our experience says that any substance can be melted. The whole history of civilization testifies to this. The discovery of the melting of matter was one of the greatest inventions in the development of mankind. But melting is not an easy process. When conducting it, many questions arise, and one of them is about how much coal (peat, firewood, gas) is needed to melt a piece of iron or copper. And here again we have to turn to the concept of "specific heat of fusion."
If we recall how the melting takes place, we can distinguish several stages. Take lead as an example. At the first stage, lead is heated, the temperature rises to 327 degrees Celsius (melting point). After melting has begun, nothing happens for a long time.
The temperature of lead, despite the heat supplied to it, remains constant and remains so until the whole process is over. And only after that, with continued heating, the temperature begins to rise again. Some conclusions follow from the observed picture. In a solid, all molecules are in a specific order and are tightly bound to neighboring molecules.
In order for them to move freely to another place, the bonds with neighboring molecules must be broken, which happens during the melting process. To do this, the body must pass a certain rate of heat, called the heat of fusion. Each substance will require a different amount of heat. The reason is due to such a property of a substance as specific heat of fusion, which is defined as the amount of heat spent on the melting of one kilogram of a substance. The unit is joule / kilogram.
As already mentioned, for each material this value is different. The specific heat of fusion of lead differs from the same value for ice. And here comes a very curious moment. The specific heat of fusion of steel averages 85 kJ / kg, while for water (ice) the same parameter averages 335 kJ / kg. Ice has a high value of this parameter can be considered a great gift from nature.
Indeed, thanks to this, all the snow, ice does not melt instantly, but everything happens for a long time. Otherwise, the snow would melt very quickly, and the floods would be more watery and destructive. In addition, such unique properties of water contribute to the stabilization of the climate on the planet.
There are tables with data on the specific heat of fusion of individual materials. Knowing this value, it is calculated how much heat is needed in order to melt the material, and to determine how much fuel is needed for melting. If the body is heated to the melting point, then heat is needed only for melting, and if its temperature is lower than the melting point, then heat is needed to heat the substance to the melting point.
Such calculations are extremely useful in industry for calculating production costs.
By the way, when the molten substance cools, the process of crystallization is reversed to melting. In this case, when the substance cools, the broken bonds between the molecules are restored and heat is released.
Considering the process of melting of a substance and the phenomena taking place at the same time, such a concept as specific heat of fusion was defined. A comparison of this indicator for different substances is carried out, it is determined how the high value of this parameter in ice has a beneficial effect on the climate of the planet.