Self-Driven Particle Model 

Self-Driven Particle Model is a physics simulation model. It is made in Java so you can run it directly from the website or on Windows, Linux or Mac OS X. Unlike other simulations by PheT, this one is more of a tutorial and it is very interactive. It has lots of text and explanations on screen and it guides you step by step. The first few steps you have test audio and read a small introduction. Later on, you start creating particles and the tutorial shows how they are influenced by other neighbouring particles in an non-random case. When two particles "see" each other, they start moving in the average direction. The following step of the tutorial lets you increase the randomness to see how that affects the movement of the particles that are on the screen. Following that, you can add more particles and study their impact on each other.

All in all, this simulation or tutorial proves to be very intuitive and all the information on the screen helps a lot in getting the point through to students. The simulation was smooth during my time with it and I love that you don't even have to install the app.