Children usually begin to understand that a substance called air is all around us after age three, but they don’t grasp that air is matter until age five, or even older. They may learn that “air is a gas” but have difficulty naming the substance that fills a soap bubble or explaining how a balloon expands, and they don’t understand where a gas released by opening a soda or mixing baking soda and vinegar comes from or where it goes. Yet, amid these ideas, early childhood is rich with opportunities for students to experience a range of gas behaviors; even if they can’t name or explain them. The lesson in this month’s column allows students to experience air’s mass and the force it can exert on objects.