"Chemical expansion" occurs when some ceramics expand upon releasing oxygen. Their ability to effectively "breathe" oxygen makes them of use in sustainable energy conversion/storage devices like solid oxide cells. However, chemical expansion during use causes cracks in these brittle materials, a problem for durability. Therefore chemical expansion must be better understood so that materials with minimal chemical expansion can be designed. In this work neutron diffraction will be applied in realistic operating conditions to perovskite-structured oxides to investigate how a particular structural aspect (long-range oxygen ordering) impacts the chemical expansion behavior. Lattice expansion, changes in atomic positions, and oxygen content during oxygen loss will be monitored and compared to prior simulations and overall (bulk) expansion measurements when oxygen is ordered vs. disordered.