How changes are classified — fast or slow, reversible or permanent — and how a physical change differs from a chemical change that forms new substances.
What happens to the composition of a substance when it undergoes a physical change?
Pure substances, elements, compounds, mixtures and methods of separating mixtures.
History of the atom, sub-atomic particles, electronic configuration, valence electrons and ions.
Chemical symbols, valency, chemical formulae, ions, and writing and balancing chemical equations.
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