Build Your Own Hoffman Apparatus

DYI Hoffman Apparatus

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.  

Time required: 

If the Hoffman apparatus is built ahead of time (this takes about 5 minutes for each one if the teacher builds them), then the activity and discussion should take less than a 45 minute period.  

Soap Making

preview graphic of soap samples

My first year teaching chemistry, I was looking for a soap-making lab or activity that I could run in my chemistry class with 25-30 students working at the same time. I usually do this activity right before spring break, as it provides enough time for the soap to harden and cure (high school students are impatient to use their soaps right away, which you should not do with cold process soap). I have used the activity at different points in the curriculum: during intermolecular forces, during acids and bases, and during stoichiometry. Although I know teachers who use soap making as a project during their stoichiometry unit, I chose to not emphasize the calculations as it would require more time than I have available. Simply making the soap easily fits in a 45-minute period.

Time required: 

45 minutes to just make the soap. Discussion of key concepts may take another class period.

Increasing Access to Stoichiometry Through Differentiated In-Class Practice

Stoichiometry resources

In a recent post, I shared sample quiz questions as to how I have differentiated assessment within the mole unit. Here, I share a specific multi-day sequence within the stoichiometry unit. I have written extensively about the project that drives this unit (within the following blog posts: Why consider trying project based learning?, Backwards planning your PBL unit -­ An Overview of an Entire Unit and What ARE my students actually learning during this long term project (PBL)?), but very little about specific learning tasks. Below is a two day sequence of stoichiometry practice that I set up in my classroom. Stations are set up around the room and students rotate as necessary.

Time required: 

POGIL: ~1 hour

Lecture: ~30 minutes

Mastery check, differentiated practice, project planning: ~2 hours

Acid, Base, pH and Food Chemistry


I try to examine activities an multiple levels. First on the list, I want to know if my students will be engaged and learn something. Second, how difficult is it for me as a teacher to actually pull it off? One of the most important questions...are the students learning chemistry or just having fun? This is the first year I have attempted the following activity.  Students were engaged in the real world connection, they asked questions, it transitioned into some chemistry concepts and even some parents got involved. The activity involved acid, bases, pH and food.

Time required: 

An evening of baking (about an hour at home) and a day in class.

Demonstration: Reaction of Magnesium and Silver Nitrate

Starting materials for demonstration

I found a version of this demonstration online a couple of years ago. I admit, when I first tried it with my class it was mostly for a crowd pleaser to demonstrate the activity series of metals, but I then became very intrigued by the processes occurring. The original source only referenced the “single replacement reaction” between Mg(s) and AgNO3(aq). Therefore, when I saw a grayish product (silver) I was not surprised. However, I was surprised by the white flash and the production of a white product, which were reminiscent of the classic combustion of magnesium demonstration. This led to some research and my conclusions that follow. Read through to the end and you will find a video of the demo.

Time required: 

30 minutes including preparation time.