Three gases, one consisting of monatomic molecules, the second consisting of diatomic molecules, and the third consisting of polyatomic molecules, are in thermal equilibrium with each other and remains in thermal equilibrium as the temperature is raised. All have the same number of molecules. The gases with the least and greatest internal energy are respectively:

Question

Quizplus · Accepted Answer

The internal energy of a gas depends on its temperature and the degrees of freedom of its molecules. Monatomic molecules have only translational degrees of freedom, whereas diatomic molecules have both translational and rotational degrees of freedom. Polyatomic molecules have even more degrees of freedom, including vibrational. As the temperature is raised, the degrees of freedom available to the molecules increase, causing the internal energy of each gas to increase. However, since the monatomic gas has the fewest degrees of freedom, it will have the least internal energy. Conversely, the polyatomic gas has the most degrees of freedom and will have the greatest internal energy. Therefore, the best choice is B, with the monatomic gas having the least internal energy and the polyatomic gas having the greatest internal energy.

Three Gases, One Consisting of Monatomic Molecules, the Second Consisting