The University of Colorado at Boulder has created engaging FREE simulations for many topics in math and science.
This is a FREE worksheet using screen shots taken from the website. Most of the directions are in pictorial form - a form that my 8th grader at home was able to follow with minimal instruction. There is a clickable link at the bottom of the page, or you can follow the pictorial instructions in the document to access the on-line simulation.
If you enjoy the sim and this worksheet, please donate to the UC Boulder PhET program (information on how to donate is on the PhET web site) so they can create more terrific FREE simulations in html5! (BTW- I have NO relationship with the PhET program EXCEPT as a grateful user of their products and a small time donor...)
I am willing to create more FREE worksheets like this one for PhET sims in html5. If there is a topic you'd like to see, ask on my store's question page and I'll try to answer most requests. All future PhET worksheets created and published by me will be FREE, unless you choose to donate to UC Boulder... I will post these on the PhET website as "teacher resources", as well.
This one works well with the Concentration PhET.
PS - If the version changes and my sheet no longer resembles the program, please let me know and I will update my sheet! Thanks!