A sorption experiment using a gas chromatograph is described that can help students understand the "molecular-shape selectivity" behavior of zeolites in the subnano regime. Hexane isomers are used as probe molecules to demonstrate the sorption phenomena. In the experiment, a zeolite adsorbs certain hexane isomers with molecular sizes smaller than its pore opening and rejects the isomers with greater molecular size. The sorption protocol is versatile and can be used in creative ways. Students can choose adsorbate-adsorbent pairs from 8-membered oxygen rings (8-MR), 10-MR, 12-MR zeolites and hexane isomers to build their own experimental protocol. The experiment can be used as an undergraduate analytical or physical chemistry experiment. (Contains 8 figures.)