Abundances with respect to total H for selected OH-group bearing molecules during the collapse stage and subsequent warm-up using the slow warm-up model. Solid lines indicate gas-phase species; dotted lines of the same colors indicate the same species on the dust grains. Panel a: stage 1 (collapse) model results, plotted linearly against time. The dust temperature is shown on the top axis, with an initial value of ~14.7 K, which falls to a minimum of 8 K, while the gas temperature is held at 10 K throughout the collapse model. Panel b: stage 2 (warm up) model results, plotted logarithmically against time. Time values correspond to the time during the warm-up stage, which are plotted beginning 2 × 10⁵ yr into the warm up. The top axis shows the gas and dust temperatures, which are identical at this point in the model.