How do you teach dehydration synthesis and hydrolysis? These two terms can be really hard for students to understand and visualize. Some students struggle with “monomer” and “polymer” too. That’s why when I teach this lesson, I break out the pop beads!
Why I love the pop beads:
1. They have an orientation. One side has a bump and one side has a hole, just like real monomers that students learn about in the biochemistry unit of high school biology. Atoms don’t have an orientation, but when they are arranged in molecules like monosaccharides, amino acids, fatty acids, or nucleotides, the molecules DO have sides. They aren’t just blobs that stick together. They have a particular spot that connects to a different particular spot on another monomer, just like the pop beads.
2. Pop beads are something that everyone has encountered at some point in their life, often as a young child, and students have fond memories of them. The biochemistry unit is definitely not a unit typically full of warm and fuzzy memories of childhood, so introducing pop beads near the beginning of this unit (and the beginning of the year) helps students to really connect with the material.
3. They are so tactile! I have and use this set but you could totally buy a cheaper set like this one and buy 2 if you want to have more for each student to play with. I really like this one too because of the different shapes and the number of pieces and I’m thinking of getting it when I go back to teaching in a few years. There is just something mesmerizing and oddly satisfying about the sound they make when you pop them on and off a chain of them. Watch the video below to see what I mean. (Links to bead sets are amazon affiliate links, because people have asked me where I got my teaching resources and if I am linking to a product, I may as well use an affiliate link.)
When I teach about hydrolysis and synthesis reactions, I do the following:
First, I tell them, hooray! We’re going to play with some new toys today. Nothing excites high school students like new toys. I open up the pop beads and I hand each student a few of them (depending on how many beads I have and how many students I have in the class). They love them. They get to play for a minute or two as I hand them around.
Second, I tell them that these pop beads each represent a “monomer”. We talk about what each monomer has (a bump and a hole). Then I have them connect two of them together and we name those “dimers”. Then, they connect a bunch together to form a “polymer”. Then I draw out a reaction on the board like this:
Monomer + Monomer = Dimer
And then I tell them that something is missing in the reaction. Whenever you put two monomers together to form a chain (or a longer chain), a water molecule forms (and I explain dehydration synthesis).
Monomer + Monomer = Dimer + H2O
I write it on the board and I encourage them to take their beads apart, then put them back together and say dehydration synthesis each time they “pop” one onto a chain.
Then I repeat the same process to teach them hydrolysis.
At the end of the class period, they all know the following terms: monomer, dimer, polymer, dehydration synthesis reaction, and hydrolysis reaction. Each of them can also write a simple reaction out for each type!
How do you like to teach hydrolysis and synthesis reactions? Let me know in the comments below!