Gas adsorption on porous solids is a topic that is often discussed in an undergraduate chemistry or chemical engineering course. The idea of porosity and gas adsorption on a porous solid is usually discussed with adsorption isotherms recorded using commercially available equipment. This discussion can be rather abstract and can be difficult for students to visualize. Here, four demonstrations highlight the adsorption of CO2 gas on adsorbents. These simple demonstrations show gas adsorption in a dynamic way that can help students understand the properties of porous solids.