ME209.1x is a basic course in thermodynamics, designed for students of mechanical engineering. We will study the terms and concepts used in thermodynamics, with precise definitions. The three laws of thermodynamics (zeroth, first, and second) will be explored in detail, and the properties of materials will be studied. Many useful relations will be derived. The topics include: basic concepts and definitions the work interaction the first law, energy, and the heat interaction the zeroth law, temperature, and scales of temperature properties of gases and liquids, equations of state the second law, thermodynamic temperature scales, and entropy relations between properties open thermodynamic systems There will be emphasis on problem-solving. Students will need to spend significant effort on solving exercises. The course is designed for students in mechanical engineering. However, others (both engineers and scientists) are likely to find it useful. The course has also been found to be useful to teachers of thermodynamics.