What are chemistry students prone to when learning stoichiometry?

A blog I am reading every week is Math Equals Love. Sarah Carter, math and chemistry teacher in Oklahoma, writes in exquisite detail about the things she is trying in her classroom. Every time I read it, I wish she had been one of my math teachers. Sarah loves, and often features, puzzle she is using in her classroom. I, too, love puzzles and that's probably one of the reasons I love her blog. One of the things I loved best about middle school math were those cheesy, punny puzzles when solving a math problem led to a letter that led to an answer to a question involving math. I recently had to miss three days in my classroom, right as my students needed to take a big quiz over stoichiometry (the math of chemical reactions, for non-chemistry teachers), so, inspired by Sarah and middle school math, I created a puzzle for them to do in my absence.

The puzzle consists of 24 paper tiles that have a letter in the center. All the tiles also have an answer at the top of the tile. Some of the tiles have a stoichiometry problem at the bottom of the tile. Students, working in groups of 4, solve the problems and then look for the answer on the letter tiles. Finding the correct answer shows the letter that comes next in the sequence. Solving the whole puzzle correctly answers the question "What are chemistry students prone to when learning stoichiometry?" Answer: Overreactions.

The puzzle is pictured below and you can make a copy of the file here if you'd like to use it. Please attribute it to me if you share it with others.

The reason I love a puzzle is because the kids can figure out the word(s) and that helps them check if they are solving the problems correctly. The puzzle provides the feedback that they need, especially when I am absent and cannot. I am particularly proud of THIS puzzle because I built in some ways that make it challenging. The four chemical reactions in the puzzle all involve lithium and water in one way or another. Finding the limiting reactant, then, is not as simple as just looking at what is in a particular reaction and finding that tile. The extra tiles (answers but no questions) are spoilers, common mistakes that students might make when solving these types of questions. One of my students emailed me right after class to ask about a problem that her group struggled with, so I made this video to try to help.

Are you using puzzles in your classroom? I hope you'll share them and inspire others.