atom: the smallest basic unit of matter
• there are more than 100 types of atoms
• matter does not contain atoms…it is atoms!
• although you cannot see them, atoms do have mass.
500,000,000,000,000,000,000,000 atoms fit into a
• molecule: a particle that is formed when 2 or
more atoms bond together
• it can be made of atoms that are different or
• example: 2 hydrogen atoms bond with an oxygen
This molecule is water!
Molecules: Some Facts
• What would happen if you divided water to find its
• Eventually you would have only one molecule of
water…then what happens if you divide that?
• You no longer have water! You have “H” and “O”, 2
• Molecules made of different numbers of same atom
are completely different substances: 2 oxygen atoms
bonded together is an oxygen gas molecule but 3
oxygen atoms bonded together is an ozone molecule.
• Atoms and molecules are always in motion!
Matter can be pure or mixed
• most substances around you are mixed,
• element: a substance that contains only a single
type of atom
• elements are found on Periodic Table
• there are 118 elements on most Periodic Tables
gold atoms gold coin
• COMPOUND : a substance that consists of 2 or
more different types of atoms bonded together
• a compound can be very different than the
elements that make it
• mixture: a combination of different substances that
remain the same individual substances and can be
separated by physical means
• examples: fruit salad, kool-aid
Comparing Mixtures and Compounds
• The substances in mixtures remain the same
substances. Compounds are new substances
formed by atoms that bond together.
• Mixtures can be separated by physical means.
Compounds can only be separated by
breaking the bonds between atoms.
Types of mixtures
• heterogenous: the properties are different in
different areas of the mixture
• homogenous: when substances are evenly
spread throughout a mixture, you cannot tell
one part of the mixture from another