Cracking the SAT Chemistry Subject Test
- A Water’s vapor pressure (its tendency to evaporate) is low compared to
other similarly sized molecules. What keeps molecules together in the
liquid state? Intermolecular forces do, and the intermolecular force most
prevalent in water is hydrogen bonding. Since hydrogen bonds are a
relatively strong intermolecular force, water molecules are significantly
attracted to each other, and water does not evaporate readily.
- B You might be asking yourself: purplish vapor? How am I supposed to
know that? Unfortunately there will be a few questions on the test that
will test your familiarity with the properties of certain substances. We
hope your experiences in chemistry lab will carry you through. If not,
don’t panic. You’ll see only a few of these types of questions. Iodine is a
grayish-purple solid that gives off a similarly colored vapor as it
sublimes.
- E If you don’t know that graphite, a form of carbon, can conduct
electricity, you can still get the answer by eliminating the other choices.
Choices (A) and (C) are ionic solids—they can conduct electricity in
solution or in the molten state, but not as solids. Choices (B) and (D)
(table sugar) are molecular solids. You wouldn’t expect molecular solids
to be particularly conductive. That leaves graphite, which is a network
solid.
- C If you’ve dissolved sodium hydroxide pellets in a beaker of water and
felt the side of the beaker, you know that the process gives off heat.
Part B
- T, T Use the divide and conquer strategy. Carbon is a nonmetal, so
statement I is true. Do carbon atoms bond with each other? They sure
do. Otherwise we wouldn’t have oils, waxes, fossil fuels, diamonds,
and literally thousands of different substances. Now, does the sentence
make sense? No. Metal atoms can also bond with each other, so this
ability is not unique to nonmetals. Fill in both true ovals, but not the
CE oval.
- F, T Isotopes of the same element do not have the same mass number, but
since they are the same element, their atomic numbers (the number of
