All topics: http://pindex.com/
Earth resources:
http://esseacourses.strategies.org/
http://undsci.berkeley.edu/article/alvarez_01
what natural materials are used to make things?
http://www.mineralseducationcoalition.org/pdfs/study/studyoftheearth.pdf
our webpage for student work on this topic- https://sites.google.com/site/namethatnaturalresource/
Ocean lessons:
https://seagrant.uaf.edu/marine-ed/curriculum/grade-7/investigation-3.html?task=view
Online game simulations-heat transfer. electricity. photosynthesis, heredity