5 Steps to a 5 AP Chemistry

Convert from feet to inches:

Finally, convert from inches to centimeters:

The answer will be rounded off to 2 significant figures based upon the 2.3 miles, since all

the other numbers are exact:

Sometimes on the AP exam, only setups will be given as possible answers. Write the correct

setup to the problem and then see which one of the answers represents your answer.

Remember: The units must cancel!

Also: Make sure that the answer is legible and reasonable!

The States of Matter

Matter can exist in one of three states: solid, liquid, or gas. A solidhas both a definite shape

and a definite volume. At the molecular level, the particles that make up a solid are close

together and many times are locked into a very regular framework called a crystal lattice.

Molecular motion exists, but it is slight.

A liquidhas a definite volume but no definite shape. It conforms to the container in

which it is placed. The particles are moving much more than in the solid. There are usually

clumps of particles moving relatively freely among other clumps.

A gashas neither definite shape nor volume. It expands to fill the container in which

it is placed. The particles move rapidly with respect to each other and act basically independ-

ently of each other.

We will indicate the state of matter that a particular substance is in by a parenthetical

s, l, or g. Thus, H 2 O(s) would represent solid water (ice), while H 2 O(g) would represent gaseous

water (steam). For a more detailed discussion of solids, liquids and gases see Chapters 8 and 12.

The Structure of the Atom

Historical Development

The first modern atomic theory was developed by John Dalton and first presented in 1808.

Dalton used the term atom(first used by Democritus) to describe the tiny, indivisible par-

ticles of an element. Dalton also thought that atoms of an element are the same and atoms

of different elements are different. In 1897, J. J. Thompson discovered the existence of the

first subatomic particle, the electron, by using magnetic and electric fields. In 1909, Robert

Millikan measured the charge on the electron in his oil drop experiment (electron charge =

−1.6022 × 10 −^19 coulombs), and from that he calculated the mass of the electron.

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46  STEP 4. Review the Knowledge You Need to Score High

KEY IDEA