Structure of liquid water: Is the two-state model operative?

► We model liquid water properties using a simplified two-state theory. ► The experimental data are reproduced well even with extremely rough assumptions. ► Compressibility of 'bulky' state decreases with temperature, which is unphysical. ► It is obvious that manipulating with assumptions would not correct this fault. ► The coexistence of only two phases in liquid water is thus questioned.