Background: Undergraduate students consistently struggle with mastering concepts related to thermodynamics. Prior work has shown that haptic technology and intensive hands-on workshops help improve learning outcomes relative to traditional lecture-based thermodynamics instruction. The current study takes a more feasible approach to improving thermal understanding by incorporating simple mechanical objects into individual problem-solving exercises. Purpose/Hypotheses: This study tests the impact of simple mechanical objects on learning outcomes (specifically, problem-solving performance and conceptual understanding) for third-year undergraduate engineering students in a thermodynamics course across a semester. Design/Method: During the semester, 119 engineering students in two sections of an undergraduate thermodynamics course completed three 15-min, self-guided problem-solving tasks, one section without and the other with a simple and relevant physical object. Performance on the tasks and improvements in thermodynamics comprehension (measured via Thermal and Transport Concept Inventory scores) were compared between the two sections. Results: Students who had a simple, relevant object available to solve three thermodynamics problems consistently outperformed their counterparts without objects, although only to statistical significance when examining the simple effects for the third problem. At the end of the semester, students who had completed the tasks with the objects displayed significantly greater improvements in thermodynamics comprehension than their peers without the relevant object. Higher mechanical aptitude facilitated the beneficial effect of object availability on comprehension improvements. Conclusion: Findings suggest that the incorporation of simple mechanical objects into active learning exercises in thermodynamics curricula could facilitate student learning in thermodynamics and potentially other abstract domains.