Determine whether the entropy increases or decreases in the third process. In the third process, heating the solid copper at a constant pressure until it melts increases the volume occupied by the copper. The molecules in the liquid form have freedom of motion and a number of positions to occupy than those in the solid form. We can therefore predict that the entropy of the system. (Describe the relationship between entropy and temperature changes. Describe the relationship between empty and phase changes. Given a chemical or physical process, predict whether entropy increases or decreases. The following decomposition reaction occurs when magnesium carbonate is heated at a constant pressure of 1 atm. MgCO_3 (s) rightarrow MgO (s) + CO_2 (g) Determine whether the entropy increases or decreases in the fourth process. The fourth process, occurring when calcium carbonate is heated at constant pressure, is given. MgCO_3 (s) rightarrow CaO (s) + CO_2 (g) The chemical equation shows that a reactant (calcium carbonate) is decomposed into a product (carbon dioxide) as well as a solid product (calcium oxide). The molecules of the gas occupy a volume than the solid, and they have freedom of motion and positions to occupy than the ions in the solids. We can therefore predict that the entropy of the system. greater or less larger or smaller increases or decreases solid, liquid, or gaseous solid, liquid, or gaseous greater or smaller greater or less more or fewer increases or decreases