In this chemistry activity, learners explore chemical reactions and their effects, including the kind of reaction in the human body that makes people burp! Specifically, learners experiment with mixing water and antacid and the resulting carbon dioxide gas bubbles produced. They also can experiment with how differing pressure affects the size of the bubbles produced. In the "Extensions" section, it is suggested that the participants use other substances and equipment to see what happens as gas is produced and expands.