Wikimedia
Wikipedia: Conservation of Mass
This site from Wilkopedia defines the law of conservation of mass. Included are links to related topics and terms used in the definition.
PBS
Pbs Teachers: Potential Energy: How Does It Work?
Describe the difference between energy in motion and at rest, and demonstrate energy's capacity for doing work. Draw a picture of water moving a turbine, and discuss other ways that a turbine might be made to move.
E-learning for Kids
E Learning for Kids: Science: Mexican Diner: What Is Energy?
Meet Carlos at his Mexican diner, and he will tell all about energy and energy transformations.
New York University
New York University: Law of Conservation of Energy
Site presents a straightforward presentation of Rutherford's work concerning the Law of Energy Conservation. Provides an adequate summary of early science on the nucleus, and includes much needed illustrations.