Gases present something of a paradox for the casual observer--they are everywhere and yet, it remains difficult to see them anywhere. The instructional sequence described in this article is an approach that the authors use with middle school students to help enhance their conceptual understanding of gases. Research has shown that these ideas can be surprisingly difficult for students to master (Johnson 1998; Stavy 1991). The authors present three activities structured as a series of exploratory, hands-on exercises and demonstrations, ordered so that they build upon one another. This sequence is consistent with the National Science Education Standards Teaching Standards B and D, and Content Standards A, B, and G for grades 5-8 (NRC 1996).