Free Science and Math Simulations

PhET: Simulations from University of Colorado.  Only HTML 5 Sims work with Chromebooks. 

Concord Consortium: Simulations for all age groups with NGSS pathfinder.  

CK12: Geared toward secondary but easy enough for elementary. Contains both chemistry and physics topics.

ASPIRE: University of Utah.  Not sure if these have HTML 5, may need a PC for these.  

Edumedia: Some are more animations but might be helpful.