States of Matter Simulator
With this simulator, students investigate the interplay between particle stickiness and thermal jiggle. Solid, liquid, and gas states are easily discernible, and melting, freezing, evaporation, and condensation are affected by changing the system temperature. Particle stickiness is controlled by selecting among neon, argon, molecular oxygen, and water.
A set of companion experiments is now available: Three Experiments for the States of Matter Simulator
Please take some extra time to illustrate these model concepts to your students:
★ The state of a sample is determined by a competition between particle "stickiness" - which encourages clustering - and "thermal jiggle" - which encourages dissociation.
★ The stickier the particles, the more thermal jiggle required to induce dissociation. This explains why the melting point of argon is higher than that of neon, and why the melting point of water is higher than that of argon, etc.
★ By changing the system energy, you can affect freezing, melting, dissociation, and condensation of the clusters. For example, it is very obvious when a crystalline cluster has been heated sufficiently to melt. Very cool and very visual.
★ To produce a stable dimer, a collision must involve three or more particles
. A collision of 2 free particles cannot produce a stable dimer, since the internal energy of the incipient dimer will always exceed its dissociation threshold. It must
fall apart. But, if a third body is involved in the collision, it can carry away some energy and thus stabilize the incipient dimer. Likewise for trimers, tetramers, etc.
★ A stable cluster remains stable until it hits something.
★ If you watch the simulation carefully, you will see that clusters are frequently metastable
, and in my opinion these metastable clusters are the interesting ones! While watching the simulation, I saw a large liquid neon cluster get nailed by a free neon atom. The cluster absorbed the colliding atom and held together! Much later, sufficient energy found its way into a dissociation channel for the the cluster to dutifully spit out a neon atom! Metastable. Very cool! We now have the student knocking on the door of some truly foundational principles, such as energy coupling and redistribution dynamics, partition functions, entropy, kinetics, etc.
★ Yet another thing to watch for in the simulation: In a relatively large cluster that is behaving "liquid-ish", there are times when some region of the cluster looks crystalline, at least for a while. These local fluctuations are very interesting IMO, and you may want to ask your students to explain why a glass of water at 3 Celsius doesn't sometimes look partially frozen. Observing local freezing in a cluster of 16 particles is a bit like drawing 3-of-a-kind from a deck of cards, whereas observing a significant part of a liquid macro-cluster in a crystalline state is like drawing a mole of 3-of-a-kinds in a row. Sure, it's possible
to see a 3-Celsius glass of water occasionally exhibit visible chunks of ice - every few quadrillion years or so - but don't waste your time watching for it!
You must have Java installed on your computer to run this simulation. To install Java, go to https://www.java.com/en/download
Once Java is installed, download this product file and unzip it to your desktop. Open the resulting folder (called "States of Matter Simulator" on your desktop), then double-click on the file "States of Matter Simulator.jar".
You don't need to uninstall anything if you wish to remove the simulator. Simply delete the enclosing folder.
Install OpenJDK. Download and unzip the product file. In the resulting folder ("States of Matter Simulator"), right-click the file named "States of Matter Simulator.jar" and change the permissions to allow execution of the file. Lastly, right-click the file and launch it with OpenJDK.
I did not create this resource, but rather I have modified an existing PhET
simulation to make it easier to follow the interaction dynamics. The original simulation is one of the many excellent simulations from PhET Colorado
. Here is a link to the original simulation.
Specifically, I reduced the number of particles and slowed their motion. I also removed several of the original features to simplify the application. Lastly, this modified simulation runs on your local computer, instead of running off the PhET server.