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CK-12 Foundation
Ck 12: The Mole Concept
[Free Registration/Login may be required to access all resource tools.] In the following online tutorial students will identify three methods for measuring the amount of matter in a sample. They will define the mole and its relationship...
Annenberg Foundation
Annenberg Learner: Isotopes, a Weighty Matter: Isotope Quiz
You will be presented with three different isotopes of the same element. See if you can calculate the atom's average relative mass.