5 Steps to a 5 AP Chemistry 2019

(^48) › STEP 4. Review the Knowledge You Need to Score High
Convert from feet to inches:

××

2.3mi

1

5,280ft

1mi

12in

1ft

Finally, convert from inches to centimeters:

×××

2.3mi

1

5,280 ft

1mi

12 in

1ft

2.54 cm

1in

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

the other numbers are exact:

2.3 mi

1

5,280 ft

1mi

12 in

1ft

2.54 cm

1in

×××=3.7×10 cm^5

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 solid has 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 liquid has 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 gas has 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 independently

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

particles 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.

KEY IDEA