A computational experiment that investigates single-walled carbon nanotubes (SWNTs) has been developed and employed in an upper-level undergraduate physical chemistry laboratory course. Computations were carried out to determine the electronic structure, radial breathing modes, and the influence of the nanotube's diameter on the curvature-induced strain. The students used a new graphical user interface to the TubeGen nanotube builder, which we have implemented as an extension to the open-source molecular editor Avogadro, to build and visualize SWNTs. Geometry optimizations, molecular orbital calculations, and frequencies were computed by an external quantum chemical program. (Contains 3 tables and 4 figures.)