Over the years, of course, I’ve tried to incorporate demos and phenomena in my chemistry course. But for kinetics and equilibrium phenomena, I found it kind of tough. So after years of trying to figure it out, I have a pretty good list of kinetics and equilibrium phenomena and demos that I like to use in my high school chemistry classroom.
If you’re more interested in a full on lab instead of simple phenomena, read more about the Elephant’s Toothpaste lab I do in my classroom.
Collision Theory
I always start out my kinetics unit by teaching collision theory. After learning the factors that affect solubility in the solutions unit, the kids usually understand this pretty quickly. But of course, showing is better than telling. I prefer to do an inquiry lab for collision theory.
In the collision theory glow sticks lab activity, students take a look at the reaction that takes place inside a glow stick. Obviously there is no reaction before the reactants come in contact when the glow stick is cracked. The students will then crack 2 glow sticks of the same size and shake just one of them. They also will check out the reaction rate (brightness) using two different sized glow sticks. Lastly, my favorite part is that they put one glow stick in a hot water bath and another in an ice bath and compare the reaction rate. This is such a fun way to see how contact, concentration and temperature affect reaction rate. Read more about the lab activity specifics here.
PE Diagrams
Potential energy diagrams make it tough to find a phenomenon. It’s a graph after all. Well, I’ve found that you could do a few things, like finding a reversible reaction like the iodine clock reaction. And I would have loved to do that, except I never had the materials for that demo. But I do have something for a super simple kinetics phenomenon!
Use just a match! The activation energy for lighting a match is whatever amount of energy YOU put into striking it. The striker panel on the box is a catalyst that reduces the amount of energy you need to put in. But, if you can strike the match on a lab table or chalkboard (those are the things I’ve found that work best) you can light the match without the help of the striker panel. Have students compare the amount of effort needed to light the match in each situation.
Be careful with this though. Once or twice I have pressed very hard on the match and both lit and snapped the match. Then the chunk of a lit match went flying through my classroom. Please make sure nobody is in the way of this match should it leave your hands.
Hess’s Law
This one will really depend on how far you take Hess’s Law. My students have always simply manipulated the reactions, like flipping them or doubling them. We never needed to learn how to add steps together. BUT I still teach that reactions are really composed of smaller steps. And with that, we watch this video where a father follows the EXACT directions his children gave him for making a peanut butter and jelly sandwich. It’s a really good analogy for a reaction mechanism and the need to be precise in the calculations and manipulations. You could even have your students attempt to write their own set of instructions!
Entropy
When we talk about entropy in my classroom, we talk about how it’s almost impossible for us to keep our rooms clean. And that’s because we are a part of nature. We favor low energy and high entropy situations. I say, “nature is messy and lazy.” And that’s a pretty good phenomenon on its own, but I also like to show this video on a backyard garden growing out of control and how a man puts in a day’s effort to clear it. It’s a perfect example of nature being messy and lazy. We address some questions:
- How did the backyard get to be so overgrown?
- What do you think the backyard would look like if he had never cleared it?
- Why did it take so long to clear the backyard?
Equilibrium
This again, the iodine clock reaction could be nice, but I think a far more tangible way for students to see equilibrium in action would be to do a simple lab using water, graduated cylinders and straws. The first graduated cylinder will have water in it, and the second will be empty. One represents the reactants and the other represents the products. Students use straws to carry water from one graduated cylinder to another at the same time. This is the forward and reverse reaction running at equal rates. Students will collect volume data from each cylinder and eventually their data will remain constant. Alas, the students have reached equilibrium. This is a great inquiry lab, but can also be done after learning equilibrium to really see it in action. I also have my students graph this data to really see the equilibrium phenomenon! This lab is currently only available in my full year lab book, but soon will be available individually so stay tuned!
Le Chatelier’s Principles
Did you know that mood rings actually work by Le Chatelier’s Principles? Mood rings make an amazing demo or phenomenon for equilibrium and Le Chatelier’s Principles. Mood rings are actually made of thermotrophic liquid crystals that change their alignment with each other and establish equilibrium based on the new temperature. Yeah, that’s a mouthful! So in layman’s terms, when the crystals are experiencing a change in temperature, they give themselves a new arrangement. We watch this video on mood rings and engage in the discuss of the chemistry of mood rings and relate that to Le Chatelier’s principles.
No Chemicals? No Problem?
When I first started teaching chemistry I was working out of an old art classroom and I didn’t have any real materials. So trying to put together good demos and phenomena for kinetics and equilibrium (and other units) was really tough. I’m so happy to be able to share these demos and phenomena with you whether you have access to chemicals and materials or not. Sometimes the quick thing is the easier thing, and sometimes, it’s all your students need to have a deep understanding of chemistry.
You can get a full printable list of these kinetics and equilibrium phenomena by clicking here.
