Back in high school, "chem" was a four-letter word to me — this Eve had no desire to hang out with that Atom! I never would have imagined that over fifteen years later, molecular chemistry would be one of my favorite units to teach. See how our exploratory unit unfolded with my photo essay from the lessons.
I did not begin our science unit with the intention of tackling ionic and covalent bonding or electron configurations. I began with the standards-based plan to cover the states of matter, phase changes, and reactions. However, as we worked through the regular sequence of lessons, my students’ questions became a powerful force. Why exactly does salt change the freezing point of water? Why does ice expand as it freezes? Why do water molecules stay together? Why do different liquids have different boiling points?
As my students’ questions piled up, I realized that this was my chance to take on a student-interest-driven unit of study. Never before were all of my students so demandingly curious about an academic subject. There was a powerful spirit of chemical curiosity in the air, and I felt compelled to respond to their questions. I got the green light from my wonderfully flexible principal to take an academic detour, picked up some middle school chemistry books to brush up on the subject, and we were off on our exploration of Why!
In order to understand why atoms behave the way they do, my students needed to learn about the three main subatomic particles: electrons, neutrons, and protons.
My students spontaneously adopted "The Atoms Family" song as our class anthem. I would hear them singing it at recess and as they headed to the bus each day. You can download the song lyrics at the The Science Spot. (Tip: Click on any photo in this post to enlarge the image.)
Next my students made edible models of atoms. We used mini marshmallows for the protons and neutrons, and raisins for the electrons. (To dye half of the marshmallows, we dipped them in a solution of food coloring and water and let them drip dry on wax paper.) We wrapped the nucleus with plastic baggies, and then punctured the bags with toothpicks to hold the electrons in place. Above is a fluorine atom with nine raisin electrons, nine blue marshmallow protons, and nine white marshmallow neutrons.
We also watched this Study Jams! video about subatomic particles.
Once my students understood the basic parts of an atom, they were ready to explore the different atoms that make up elements. My students quickly noticed that it’s difficult to keep track of all of the elements without an organized system. Several students started making their own charts and tables to keep track. They were quite happy to see that the work was already done for them when I introduced the Periodic Table of Elements.
My students color-coded their periodic tables in their notebooks as they explored groups and periods. My students also enjoyed exploring the Periodic Table of Videos by the University of Nottingham. They post videos of experiments and explanations for each element.
My students personified their favorite elements to create Periodic Table playing cards. We used Basher Books' The Periodic Table: Elements With Style for inspiration. (Their Web site is also a fun resource.)
Sprightly little electrons are so important for understanding how atoms behave around one another, so we spent several lessons learning about various models for picturing electron energy levels.
Sodium chloride (table salt) provided a relatable context for learning about ionic bonding. My students were surprised when they observed that all of their salt grains were actually tiny cubes. They explored why salt takes this shape, and they realized it has to do with the bonding pattern between sodium and chloride.
Here you can see the supplies for our salt exploration. My students began with cups of coarse salt, a hand lens, and black paper squares. When they were ready to begin building their sodium chloride "molecules," each table received a bowl with gumdrops and toothpicks.
I used this lesson plan from the American Chemical Society to guide my students through an exploration of the ionic bonding that occurs between sodium and chloride molecules. I adapted their student worksheet to create a single foldable page for my students' science notebooks. After my students understood the mechanics of ionic bonding, they used small and large gumdrops to build models of sodium chloride crystals. (The larger gumdrops represent negative chlorine ions, and the smaller gumdrops represent positive sodium ions.)
We first explored covalent bonding on the computer with an interactive molecule-building applet. Then my students worked in pairs to build interesting molecules using candy.
Two students show off their finished caffeine molecule.
We used gumdrops, marshmallows, and toothpicks to build molecular models. (We used marshmallows for the smaller hydrogen atoms.) The students chose their molecules from a set of molecule cards that I printed from MakeItMolecular.com.
The students labeled their models and created "Key Cards" explaining how they color coded their molecules. The student on the right shows off his ethanol molecule. The other photo shows the card for his molecule.
We hung the students' molecular models from the hallway ceiling.
Polymers are fun molecules to explore with kids. From the playground tire swing to silly putty, children have plenty of experiences with polymers. “Exploring the properties of a cross-linked polymer” (i.e., playing with slime!) was an enjoyable way to end our molecular chemistry unit.
It was so exciting to watch how my students applied their understanding of molecules and molecular interactions to understand the mechanics of cross-linking polyvinyl alcohol!
To save time and have reliable results, I bought a slime-making kit from Steve Spangler Science. There are plenty of recipes for making your own polymer goop, however. The Science Bob recipe uses white glue and Borax, and the Steve Spangler recipe uses PVA and Borax. I modeled the cross-linking action between the PVA polymer strands with long chains of paper clips. This really helped my visual learners understand the reaction.
Taking a detour through the world of chemistry was well worth the time and effort. I've never seen my students quite so motivated and passionate about a subject. Many of them have continued with independent research projects on chemistry topics that are particularly interesting to them. I am thrilled that I was able to help build the background knowledge that my students needed to pursue their independent research. Exploring everything from greenhouse gases to nuclear fusion, my young chemists are off to a great start with their own research!
One student's independent research projects.
In taking this detour, I drew on a number of excellent resources. I hope some of them are helpful as you plan your own chemistry activities.