Cracking the SAT Chemistry Subject Test

MASS

Think about a sample of any type of matter, whether it’s a hunk of solid, a glass
of liquid, or a container of gas. The mass of any of these samples refers to the
amount of matter in the sample, while matter simply refers to anything that
occupies space and has mass.

To   convert     grams   to  kilograms,  just    move    the     decimal     point   three

places  to  the left.   To  convert kilograms   to  grams,  move    the decimal

point   3   places  to  the right.

585 g   =   0.585   kg

To   convert     grams   to  milligrams  or  liters  to  milliliters,    move    the

decimal three   places  to  the right.  To  convert milligrams  to  grams   or

milliliters to  liters, move    the decimal point   three   places  to  the left.

1.524   g   =   1,524   mg

                2.4 L   =   2,400   mL

Mass is measured in grams. One gram is nearly equal to the weight of a paper
clip—for heavier samples it’s often more convenient to use kilograms (1 kg =
1,000 grams), while for very small samples, it’s convenient to use milligrams (1
mg = 1/1,000 gram). For any particular substance, a sample of greater mass
means a sample with more atoms or molecules in it. (For now, think of atoms
and molecules as tiny pieces of matter. We’ll talk more about them later.) Two
different samples of the same substance that have different masses must be made
up of different numbers of atoms or molecules; for example, ten water molecules
have greater mass than seven water molecules. Eight carbon dioxide molecules
have greater mass than four carbon dioxide molecules.

For the SAT Chemistry Subject Test, there’s nothing more you need to know
about mass itself. It represents the quantity of matter that makes up a sample. It’s
usually measured in grams, kilograms, or milligrams.