1. Atoms, Elements, Molecules,& Compounds
What happens when substances combine?
8.8B Identify the properties of an atom.
8.9A Demonstrate that substances may react chemically to form new substances.

2. Atoms, Elements, Molecules,& Compounds
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Substance — Matter that has the same composition and properties throughout.
Atom means “cannot be divided” – smallest unit of element that retains properties
Element — simplest form of substance, pure substance, Listed on Periodic Table
smallest unit only one kind of atom.
Molecule — two or more atoms combined
smallest particle of a substance
May be two atoms of one element O2 N2
May also be two or more atoms of different elements CO H2O

3. Compound: more than one element combined
in definite proportion (fixed ratio)
makes new substance different from elements.
Water: H2O Carbon Dioxide: CO Sugar: C6H12O6
Substances can react and form new substances.
Changes occur during these reactions.
List the types of Chemical Changes:
Can you distinguish between elements and molecules?
Between molecules and compounds? Name the chemical reactions? Write your summary.