I was reading the Knight textbook, which stated in Chapter 16.1 (A Macroscopic Description of Matter) the following:
"The notion of three distinct phases is less useful for more complex systems. A piece of wood is solid, but liquid wood and gaseous wood don’t exist."
Can someone explain to me what is meant by "more complex" and its relationship to phase transition? That is, why can't one describe a phase transition for a piece of burning wood even though, as it appears to me, that it transitions into a gas (i.e. sublimation)?