The equilibrium probability distribution of a lattice gas with short‐range binary interaction is obtained. Numerical analysis shows the appearance of two peaks of such distribution for sufficiently low temperatures. This implies the onset of a first‐order phase transition. From the possible behaviors of the distribution (one peak, two peaks, or a ‘‘plateau’’), a splitting of the thermodynamic space of the system is reported. This splitting is macroscopically (thermodynamically) interpreted in the light of the behavior of the isotherms obtained from the thermal equation of state.