During the history of thermodynamics, scientists discovered that the heat is not a substance but a motion of matters and that the temperature of the ideal gas is proportional to its internal energy. How do the gas molecules behave in the air? The author explains the molecular mechanics of the ideal gas using a simple elastic model of the gas molecule. The author concluded that the rotation movement of the gas molecule determines its shape, pressure, and volume. It is also concluded that the rotation energy corresponds to the temperature. You can be a hero to discover a new world of thermodynamics and let us make difference in science after reading this book. Good luck, and enjoy your exploration to the thermodynamics, an exciting field in physics!