Scholastic
Scholastic: Study Jams! Science: Matter: Elements & Compounds
A video and a short quiz on elements, how they combine through chemical reactions to make compounds, and how to write the chemical formulas for water and salt.
CK-12 Foundation
Ck 12: Percent Composition and Empirical & Molecular Formulas
[Free Registration/Login may be required to access all resource tools.] In this online tutorial students will learn to calculate the percent composition of a compound either from mass data or from the chemical formula. They will use...
Purdue University
Purdue University: Elements, Compounds & Mixtures
Provides definitions and characteristics of elements, compounds, and mixtures, and gives an animated image of each.
Encyclopedia of Earth
Encyclopedia of Earth: Physics & Chemistry: Calcium
Information about the element, Calcium, atomic number 20. Covers physical and atomic properties, sources, its role in geochemical cycles, how abundant it is on the Earth, its isotopes, some compounds of calcium, and its importance to...