Entropy is given with equation:
Where $S$ - entropy, $k_b$ - Boltzmann's constant and $Ω$ - number of possible microstates.
What quantities is the number of microstates dependent on?
Suppose I have a 1 litre container, isolated from outside environment, filled with 0.5 litres of gas at 50 °K and 0.5 litres of the same gas at 100 °K, both at the same pressure p. Eventually this system will reach an equilibrium at some temperature and the entropy of the system will have increased, because heat was transferred. The volume, number of molecules and internal energy is still the same for the system, how could the entropy have increased? What has increased in the system for it to have more possible microstates?