In this activity, learners explore two properties of gases: gases take up space and exert pressure. Learners assemble two flasks and a beaker, connecting them with stoppers and tubing. They combine baking soda, water, and citric acid in a flask and then stopper the flasks. Gas (carbon dioxide) from the chemical reaction flows into a second flask, displacing colored water from the second flask into the beaker. An extension to this activity uses the gas created to put out a candle flame. This activity is currently used in the Nature of Matter Unit in OMSI's Chemistry Lab. Cost estimates are per 100 learners. For safety reasons, this activity is best suited as a demonstration for younger audiences.