Prigogine, prih GAW zhuhn, Ilya (1917-2003), a Russian-born Belgian theoretical chemist, was awarded the Nobel Prize in chemistry in 1977 for his contributions to a scientific field called nonequilibrium thermodynamics. Thermodynamics is the study of heat and other forms of energy. Equilibrium is a steady state in which such quantities as temperature and pressure remain constant. In nonequilibrium conditions, an external influence may cause these quantities to change. See Thermodynamics.