This lesson begins with a design challenge: to invent a small device that could rescue a cell phone that accidentally falls into water. A self-inflating balloon might be able to act as a flotation device to keep a cell phone from sinking or bring it up after it sinks. Students conduct a pair of chemical reactions to determine which of two acids react with baking soda to produce the most carbon dioxide gas and apply this to the flotation problem.

Skill Level: Beginner