2. Discussion on the physical chemistry of aggregates

Aggregates appear to be a special state of matter, in that they share similarities but also fundamental differences with other states of matter. It is therefore legitimate to ask whether the physical quantities characteristic of matter (such as the concept of temperature, the definition of a melting point, etc.) correctly describe aggregates or whether, on the contrary, new quantities should be defined. The answer is not immediately obvious and remains a subject of debate, despite numerous studies, some of which are presented later in this article.