Teaching thermodynamic properties of water without tears

A typical thermodynamics course begins with the familiar ideal gas law to determine the state properties. Water properties are introduced next. Considering students have already seen the ideal gas law in chemistry courses, the instruction is brief and often pertains to its engineering application with the mass-based form of the equation of state. The thermodynamic behavior of water, on the other hand, proves relatively challenging for many students. The existence of phase change within engineering conditions renders an intractable equation of state for water. Instead, we rely on property data references such as steam tables to determine state properties. This apparent disconnect between ideal gases and water, and the introduction of a new tool for property retrieval, often leads to appreciable time allocated to the instruction of water properties and subsequent struggles. This allocation of instructional time is at the expense of performing advanced thermodynamic analysis of engineering processes and cycles. Recognizing the need to quickly and effectively introduce thermodynamic properties of water and at the same time reinforce the fundamentals, a new instructional approach was implemented. The approach relied on targeted videos to (a) make the transition from ideal gas model to water properties seem less disconnected and (b) convey state relationships in a visual form, namely property charts. Two separate videos on ideal gases and water were produced with a clear overlap related to real fluids. Both videos used property charts to visualize the thermodynamic property relationships. After students watched the videos outside the lecture period, a short lecture was dedicated to the mechanics of property retrieval from a T-s chart. Following the lecture, a group activity was conducted to assess student comfort with paper-based property charts for property retrieval. When surveyed, student opinion was highly favorable towards the use of videos for instruction, review, and the visual approach. The direct outcome of the control and treatment activities showed statistically significant advantage (p-value 0.038) of this approach. Students displayed adequate competence in solving water property problems using property charts. The results also showed how the use of property charts reinforces the thermodynamic fundamentals, as opposed to the use of online databases or the steam tables. The implementation yielded a marked decrease in lecture time dedicated to introducing properties of water, allowing more time to be spent on practicing thermodynamic analytical skills. This non-traditional approach, without steam tables or online reference tools, also optimally aligned with the course learning outcomes.