Chad Hustings blogged this past school year about building his own Hoffman apparatus for each group of students. I have been using a Hoffman apparatus that had been purchased by my district before I began teaching there over 20 years ago to demonstrate electrolysis of water, but providing each student group with the ability to perform an electrolysis themselves is a powerful activity. I have used a different version of a homemade Hoffman apparatus, but after reading Chad's blog post, I decided to use a version close to his.
HS-PS3-3: Conversion of Types of Energy
This lab was written as part of the Target Inquiry program at Grand Valley State University in Michigan. Students build an electrochemical cell, learn about the symbolic equations used in electrochemistry and manipulate a model representing the particulate level of what is happening during the electrochemical process.