Touchscreen apps have the potential to teach children important early skills including oral language. However, there is little empirical data assessing the educational potential of children's apps in the app market or how apps link to theories of cognitive development to support learning. We compared popular children's apps with a learning goal (N=18) and without (N=26) using systematic evaluation tools to assess the educational potential and app features that may support learning. We also transcribed all utterances in the apps that included language with a learning goal (N=18) and without (N=12) in order to compare a number of psycholinguistic measures relating to accessibility of the language. Apps with a learning goal had higher educational potential, more opportunities for feedback, a higher proportion of ostensive feedback, and age-appropriate language to support learning and language development. Thus, we argue that selecting children's apps based on the presence of a learning goal is a good first step for selecting an educational app for pre-school age children. Nevertheless, app developers could do more to promote exploratory app use, adjust content to a child's performance, and make use of social interactions with characters onscreen in their apps to enhance the educational potential. Children's apps could also make better use of feedback to ensure that it is specific, meaningful and constructive to better facilitate learning.