What information would you need to specify the macro-state of the air in a room? What information would you need to specify the microstate?

Microstate is a term that describes the microscopic properties of a thermodynamic system.

The word "macro-state" refers to the macroscopic characteristics of a thermodynamic system.

To specify what microstate the system is in, a detailed description is needed. We can define a macro-state by specifying the value of macroscopic variable.

For typical systems, the number of microstates is very big, and they represent the system is far more particular than considered. For example, let's consider a box filled with gas or the air in a room. We have no way to measure the exact position and momentum of every gas molecule, and they are insignificant even if we could measure them. Instead, we are usually interested in a small number of macroscopic variables: the total energy of the system, the total number of gas molecules, the volume of space it takes up, etc. These physical quantities are measurable and have practical importance.

A macro-state is defined by defining the value of every macroscopic variable. The density of states is the quantity of microstates that make up a microstate. It is written as$\Omega (E,V,\dots )\Omega (E,V,\dots )$ , where the arguments are the macro-macroscopic