This lecture starts by considering a gas of N molecules enclosed in a box with a piston. By analyzing the equilibrium between the gas and the piston, the instructor demonstrates that the ideal gas law is a consequence of Newton's second law. The lecture then explores the concept of Avogadro's number and the ideal gas constant, leading to the derivation of the ideal gas law equation. The pressure of the gas is related to the change in momentum during collisions with the piston, emphasizing the average effect of molecular velocities on pressure. The isotropic nature of gases is also discussed, highlighting the absence of directional preferences in gas properties.