The empirical equations of configurational energy U-conf. and configurational heat capacity C-P,C-conf. have been derived for polymer and simple liquids including amorphous polymer liquids, rare gas liquids, and non-polar and polar liquids based on experimental data over the temperature range up to vapour-liquid critical temperature T-c. The equations obtained in this work are:U-conf. = U-0/V-0(V-V*)/V(V-0-V*) exp (V*(V-0-V)/V(V-0-V*))C-P,C-conf. = U(0)V(0)(*2)alpha(P)(V-0-V)/V-2(V-0-V*)(2) exp (V*(V-0-V)/V(V-0-V*))where V is specific volume, alpha(P) is the thermal expansion coefficient, U-0 is the minimum of U-conf., V* is V when U (conf.) = 0, and V-0 is V when U-conf. = U-0. The expressions of cohesive energy density, internal pressure P-i and the V-m at which P-i is maximum are also obtained based on the equation of configurational energy. The values of V*, V-0, V-m and U-0 used in the above equations are determined for various materials based on the experimental values of thermal pressure coefficient gamma(V) over a wide range of volume and thermodynamic equation of state given by (partial derivative U/partial derivative V)T = gamma(V)T - P. The empirical expressions for alpha(P)T and gamma(v)V are also obtained based on experimental data, which areln(alpha(P)T)(-1) = a(0) + a(1)Xln gamma V^V-gamma VC VC/gamma V^V = b0 + b1X + b2X²where X = ln((T-c - T)/T), gamma(v) is the thermal pressure coefficient, T-c is the critical temperature and gamma V-c V-c is that at critical point. Values of a(0), a(1), b(0), b(1), and b(2) are constants and are a(0) = 1.1820, a(1) = 0.8425, b(0) = - 0.1724, b(1)= 0.1520 and b(2) - 0.0255 for master curves.