These are a few tools for helping visualize middle school science. I spent a year volunteer tutoring middle school (grade 8) science students. While doing that, I created an app with a few simple demonstrations and practice tests to help them. The modules included were those that illustrated or helped practice the concepts my students
had trouble either understanding or remembering. The test module contains every test the students took.

Hot Molecules is an interactive demonstration of the effects of heating and cooling on molecular activity.

Will it float? is an interactive lab simulation for determining density.

Questions is a test-practice module for all subjects thus far covered
(phase changes, heat transfer, density, atoms,
molecules, reactions, atmosphere).

Buckets is a category builder to help understand grouping of like things on arbitrary traits

Which is Bigger? is an interactive statistics exploration, showing how much overlap there is between categories and how important sample size is.

How do population dynamics of the species populations in a food web interact? Play with the simulation and ecological and human-introduced factors. Watch out for natural disasters!

Other demonstrations and test topics are added periodically.