 Matter is composed of extremely small particles, too small to be seen with a classroom microscope, called atoms.  Atoms: smallest part of an element that has the chemical properties of the element.  A single atom has mass and takes up space.

 Electron:  smallest part of an atom  Charge: negative  Orbits around the atom (like moon around planet)  Proton:  Postive charge  In the nucleus of the atom  # of protons defines the atom  Neutron:  No charge because they are neutral  Nucleus of atom: made of neutrons and protons

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 Elements: pure substances that cannot be changed into simpler substances.  Elements are composed of one kind of atom.  Ex: Gold, Oxygen, Silver, Helium, Hydrogen  All elements found on periodic table

 Pure substances that are composed of two or more types of elements that are chemically combined.  Compounds can only be changed into simpler substances called elements by chemical changes.  One way that two or more atoms can combine is to form a molecule.  Ex: H 2 O, CO 2, C 6 H 12 O 6

 Composed of two or more different substances that retain their own individual properties  Combined by physical means  Can be separated by physical means (filtration, sifting, or evaporation).  Mixture may be heterogeneous or homogeneous.

 heterogeneous mixture  Not uniform (same) throughout  Substances can be visibly distinguished  Ex: Salad, bag of sand and rocks  homogeneous mixture  Uniform throughout  Substances can not be visibly distinguished  Another name = solution  Ex: Salt water and kool aid **Brain pop