A microstate is a state of a physical system described at the finest level of detail. A macrostate is a state of a physical system that is described in terms of the systems overall or average properties at a macroscopic level. A macrostate will generally consist of many different microstates. In defining a macrostate we ignore what is going on at the microscopic (atomic/molecular) level.
Suppose 24 students are enrolled in a class. For simplicity let’s assume that any student who is present is sitting completely still at his or her assigned seat, facing forward (so we don’t have to worry about students being in different locations, having different motions, etc.).
1. Which of the following would constitute a macrostate description of the class attendance and which would constitute a microstate description.
a. A list of the names of each student present today.
b. The number of students in attendance.

a. A list of the names of each student present today. (microstate)

b. The number of students in attendance. (macrostate)

Explanation:

You can fins the answer to this question by comparing the situation of the problem with a system of molecules with discrete energy.

Without importance of which molecules have a specific energy, but rather, what is the total amount of energy, you can get for different configurations of energy the same amount of the total energy. If different configurations of the energies of the molecules give you the same total energy of the system, you say that the macrostate is the same. In the case of the classroom, it does not matter how are distributed the students in the class, the total number of students is always the same. The macrostate is the same for what ever organization of the students in the class.

If you would interested in the energy of each molecules, you will obtain different configurations. In the case of the classroom. The names of the student will define a microstate because in this case there are many configurations.

a. A list of the names of each student present today. (microstate)

b. The number of students in attendance. (macrostate)

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