1. Figure 21.1  A cubical box with sides of length d containing an ideal gas. The molecule shown moves with velocity vi.
Fig. 21.1, p.641

2. Active Figure 21.2  A molecule makes an elastic collision with the wall of the container. Its x component of momentum is reversed, while its y component remains unchanged. In this construction, we assume that the molecule moves in the xy plane.
At the Active Figures link at you can observe molecules within a container making collisions with the walls of the container and with each other.
Fig. 21.2, p.642

3. Table 21.1, p.645

4. Table 21.2, p.647

5. Figure 21.3  An ideal gas is taken from one isotherm at temperature T to another at temperature T + ∆T along three different paths.
Fig. 21.3, p.646

6. Active Figure 21.4  Energy is transferred by heat to an ideal gas in two ways. For the constant-volume path if, all the energy goes into increasing the internal energy of the gas because no work is done. Along the constant-pressure path if’, part of the energy transferred in by heat is transferred out by work.
At the Active Figures link at you can choose initial and final temperatures for one mole of an ideal gas undergoing constant-volume and constant pressure processes and measure Q, W, ∆Eint, CV, and CP.
Fig. 21.4, p.647

7. Figure 21. 5 The PV diagram for an adiabatic compression
Figure 21.5  The PV diagram for an adiabatic compression. Note that Tf > Ti in this process, so the temperature of the gas increases.
Fig. 21.5, p.650

8. Figure 21.6  Possible motions of a diatomic molecule: (a) translational motion of the center of mass, (b) rotational motion about the various axes, and (c) vibrational motion along the molecular axis.
Fig. 21.6, p.651

9. Figure 21.6  Possible motions of a diatomic molecule: (c) vibrational motion along the molecular axis.
Fig. 21.6c, p.651

10. Figure 21.6  Possible motions of a diatomic molecule: (a) translational motion of the center of mass.
Fig. 21.6a, p.651

11. Figure 21.6  Possible motions of a diatomic molecule: (b) rotational motion about the various axes.
Fig. 21.6b, p.651

12. Figure 21.7  The molar specific heat of hydrogen as a function of temperature. The horizontal scale is logarithmic. Note that hydrogen liquefies at 20 K.
Fig. 21.7, p.652

13. Fig. P21.26, p.662

14. Figure An energy level diagram for vibrational and rotational states of a diatomic molecule. Note that the rotational states lie closer together in energy than the vibrational states.
Fig. 21.8, p.653

15. Figure 21. 9 Molar specific heat of four solids
Figure 21.9  Molar specific heat of four solids. As T approaches zero, the molar specific heat also approaches zero. 
Fig. 21.9, p.654

16. Figure 21.10  Energy level diagram for a gas whose atoms can occupy two energy states.
Fig , p.655

17. Active Figure 21.11  The speed distribution of gas molecules at some temperature. The number of molecules having speeds in the range v to v + dv is equal to the area of the shaded rectangle, Nvdv. The function Nv approaches zero as v approaches infinity.
At the Active Figures link at you can move the blue triangle and measure the number of molecules with speed within a small range.
Fig , p.656

18. Active Figure 21.12  The speed distribution function for 105 nitrogen molecules at 300 K and 900 K. The total area under either curve is equal to the total number of molecules, which in this case equals 105. Note that vrms > v > vmp.
At the Active Figures link at you can set the desired temperature and see the effect on the distribution curve.
Fig , p.657

19. Figure 21.13  A molecule moving through a gas collides with other molecules in a random fashion. This behavior is sometimes referred to as a random-walk process. The mean free path increases as the number of molecules per unit volume decreases. Note that the motion is not limited to the plane of the paper.
Fig , p.658

20. Figure 21.14  (a) Two spherical molecules, each of diameter d and moving along vertical paths, collide if their centers are within a distance d of each other. (b) The collision between the two molecules is equivalent to a point molecule’s colliding with a molecule having an effective diameter of 2d.
Fig , p.658

21. Figure 21.15  In a time interval ∆t, a molecule of effective diameter 2d sweeps out a cylinder of length v where vΔt is its average speed. In this time interval, it collides with every point molecule within this cylinder.
Fig , p.658

22. Fig. P21.32, p.663

23. Fig. P21.32a, p.663

24. Fig. P21.32b, p.663

25. Fig. P21.35, p.663

26. Fig. P21.67, p.666