During the American Revolution, you are in charge of uncovering a message written in invisible ink.
![A letter from Benjamin Thompson to an Unidentified Recipient, May 6, 1775. University of Michigan, Clements Library.](/pbl/sites/files/pbl/styles/full_width_m/public/shared/Benjamin%20Thompson%20Letter%20to%20an%20Unidentified%20Recipient%2C%20May%206%2C%201775.%20University%20of%20Michigan%20Clements%20Library.jpg.webp?itok=CrmQKiEJ)
Problem written by: Stephanie Leighton, Taras Skotar, Yu-Sheng Chang, and LiXuan Wong
Curriculum items covered: Acid-base reactions, redox reactions, WHMIS.