The goal of the tutorial is to get an overview over Modelica libraries for thermodynamic system modelling and show how to make use of Modelica's unique features in thermodynamics modelling. Compared to traditional, specialized flow sheeting tools, Modelica offers increased flexibility. The new Media and Fluid libraries make this flexibility accessible without the drawback of laborious model implementation. We will explain the design ideas behind the libraries and, through a series of hands-on exercises, learn to use the libraries for simple examples. Using these examples, we will investigate typical modelling trade-offs in thermodynamics between models intended for component design use and models intended for system design use. The same examples will be used to demonstrate typical numerical pitfalls in thermo-fluid systems.