We investigated the relation between work function and the adsorption structure of dicarboxylic acids (organic molecules) such as succinic acid (HOOC-CH2-CH2-COOH) and an adipic acid (HOOC-(CH2)(4) COOH) on a Cu(1 1 0) surface (electrode) as a function of the surface temperature using a Kelvin probe (KP). The work function changes of the two acids are similar. The work function increases by adsorption at room temperature due to ionization of molecules and then decreases with increasing temperature until 450 K due to the effects of change in the dipole moment of the conformational change of the molecule. From 450 to 600 K, the work function is constant because of competition between desorption and change in the dipole moment of molecules. It then reached the clean-surface value. Experiments clarified that the work function was affected by the adsorbed difference in conformation of molecules. (C) 2008 Elsevier B. V. All rights reserved.