Background: In STEM education, tasks are essential for organizing and designing teaching-learning processes, as they give concrete form to curricular goals and content standards. Tasks that build on each other and initiate a learning process are particularly effective. Tasks are often specified according to their function (confrontation, development, exercises, etc.). Confrontation tasks--problem-solving situations--are particularly suitable as mediators between learners' daily life experiences and the competencies defined by educational standards. Their intention is to evoke emotions and curiosity, as well as to promote cognitive activation and competency acquisition by addressing various task features such as learners' conceptions and the possibility of multiple solution ideas. Furthermore, confrontation tasks present a novel context for the learner, are open in nature, and are relatively complex; they are, therefore, expected to elicit aspects of epistemic emotions. However, the role of epistemic emotions in confrontation tasks is under-researched. Methods: The study examines the relationship between epistemic curiosity about finding solutions and content understanding and confusion, astonishment, and boredom in the context of 16 confrontation tasks from the STEM field. For this purpose, 1360 learners (50% female, in Grades 3 to 6) were questioned about one to three STEM tasks. To investigate the relationships, a multilevel structural equation model (MSEM) was used, accounting for the nested data structure. Results: Findings from the MSEM show that in the nested data structure with crossed random factors, as theoretically assumed, astonishment was identified as a positive predictor of epistemic curiosity regarding both finding solutions and content understanding, while boredom was identified as a negative predictor. The hypothesis that confusion was positively associated with epistemic curiosity could only be partially confirmed with the available data. Conclusions: This study presents new evidence on the complex interactions between different epistemic emotions in STEM problem-solving situations, specifically in confrontation tasks. The results underscore the value of promoting positive emotions such as astonishment, as they positively relate to epistemic curiosity about finding solutions, and content understanding. Astonishment could serve as a gateway to learning opportunities, motivating learners to explore new information and fill knowledge gaps.