For example, the molar heat capacity of nitrogen N 2 at constant volume is c V , m = 20.6 J ⋅ ⋅ K − − 1 ⋅ ⋅ m o l − − 1 (at 15 °C, 1 atm), which is 2.49 R . That is the value expected from theory if each molecule had 5 degrees of freedom. These turn out to be three degrees of the molecule's velocity vector, plus two degrees from its rotation about an axis through the center of mass and perpendicular to the line of the two atoms. Because of those two extra degrees of freedom, the specific heat capacity c V of N 2 (736 J⋅K ⋅kg) is greater than that of an hypothetical monatomic gas with the same molecular mass 28 (445 J⋅K ⋅kg), by a factor of ⁠ 5 / 3 ⁠.