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Museum of Science
Museum of Science and Industry: Online Science: Activities: What Goes Around
An activity where students take on the roles of parts of the circulatory system, and simulate the transport of nutrients, oxygen, and carbon dioxide through the blood stream.
Ducksters
Ducksters: Science for Kids: Earth's Atmosphere
Kids learn about the science of the Earth's Atmosphere. Carbon dioxide, Oxygen, Nitrogen and more make up clouds and weather.