Explore the fundamental concepts of thermodynamics in this comprehensive lecture from Yale University's Fundamentals of Physics course. Delve into the nature of heat, its generation, and measurement techniques. Gain a deep understanding of the Boltzmann Constant and its significance. Examine the microscopic interpretation of temperature and its implications. Investigate the molecular mechanics behind phase changes and the Maxwell-Boltzmann distribution. Learn about quasi-static processes and their importance in thermodynamic systems. Conclude with an in-depth exploration of internal energy and the First Law of Thermodynamics. This 1-hour 15-minute lecture provides a solid foundation for understanding the core principles of thermodynamics and their applications in physics.