Miller, Kenneth R., and Levin, Joseph S.
Biology: Foundation Edition.
New Jersey: Person Education, Inc., 2010.
A great introductory biology resource for students to learn the basics.
http://www.bbc.co.uk/schools/gcsebitesize/science/ocr_gateway_pre_2011/rocks_metals/7_faster_slower1.shtml
An easy to follow walkthrough of the basics of collision theory.
http://www.learningliftoff.com/high-school-science-learning-activity-collision-theory/#.VZN1tRNViko
An interactive collision theory web application.