Much research has been published that describes the misconceptions students have about gases; however, not much research has been published that suggests how to change these misconceptions. The action research presented in this article examined how using laboratories to contradict students' preconceived ideas would affect their learning. High school students took a pretest to identify their misconceptions. The results of the pretest revealed that students' largest misconceptions were that they believed gases weighed less than solids and liquids and that they thought water decomposed when boiled. A lab and a demonstration were developed to contradict these incorrect ideas. The approach taken with a group of high school students to identify the misconceptions and to develop laboratories to contradict the problematic ideas is described. (Contains 3 figures.)