According to the definition, surface tension could be affected not only by intermolecular interaction but also by molecular area. However, in chemistry textbooks, surface tension is mainly explained only in terms of intermolecular interaction. Although the existing surface tension concept in the textbooks can lead to a variety of counterexamples, research on undergraduates' responses to surface tension anomalies is rare. In this study, we had 16 undergraduates experience an anomalous surface tension experiment and analyzed how they responded to the anomalous data and whether their explanations had met conditions for accommodation. As a result, among the 16 participants, only one student (rejection response) retained her existing conception (i.e., surface tension is proportional only to the intermolecular interaction), and the rest of the students tried to explain the anomaly in their own ways (theory change, peripheral theory change, and abeyance responses). In particular, only the six students who considered both intermolecular interaction and molecular area properly showed a theory change response that matched conditions for accommodation (dissatisfaction, intelligibility, and plausibility). The results of the study imply that the surface tension concept considering both intermolecular interaction and molecular area might be an alternative to the existing concept in chemistry education.