Measuring means finding a number that describes the size of something.
The mass of an object measures how much "stuff" (or matter) an object contains. The mass of an object is connected to its weight. We use mass units to specify an object's mass.
The most popular measurement system within the scientific community is the metric system. Within the metric system, the most common units of measurement are called base units.
The base unit of mass is the gram, which we denote using the symbol "." The object below has a mass of exactly
We can measure the mass of an object using weighing scales. To measure an object's mass, we first place it on one side of the weighing scales. Then, we put masses on the other side until the scales balance perfectly.
In this example, we have an object on the left scale and sixteen masses on the right scale. Since the scales are perfectly balanced, the object's mass is
It's convenient to define new units of measurement from the base unit. The most common variations for mass units are shown below:
| Name | Symbol | Conversion |
|---|---|---|
| Kilogram | ||
| Gram | Base Unit | |
| Milligram |
Let's give some examples of each unit, going from the largest (or "heaviest") unit to the smallest (or "lightest") unit :
A regular bag of sugar has a mass of around
A single postage stamp has a mass of around
A single grain of sand has a mass of around
Important: Each metric symbol for mass ends in "", the base unit.
Suppose we want to measure the mass of an ant. Which of the following metric units could we use?
A table showing the metric units of mass is given below.
| Name | Symbol |
|---|---|
| Kilogram | |
| Gram | |
| Milligram |
Therefore, from the given options, the only unit of mass is
Suppose we want to measure the mass of a mouse. Which metric unit could we use?
|
a
|
$\textrm{m}$ |
|
b
|
$\textrm{g}$ |
|
c
|
$\textrm{km}$ |
|
d
|
$\textrm{mm}$ |
|
e
|
$\textrm{s}$ |
Suppose we want to measure the mass of a feather. Which metric unit could we use?
|
a
|
$\textrm{ms}$ |
|
b
|
$\textrm{m}$ |
|
c
|
$\textrm{mm}$ |
|
d
|
$\textrm{s}$ |
|
e
|
$\textrm{mg}$ |
Let's recall the table that relates metric units of mass.
| Name | Symbol | Conversion |
|---|---|---|
| Kilogram | ||
| Gram | Base Unit | |
| Milligram |
Important: Symbols in the metric system follow a consistent set of prefix rules, which we explain below. If you find these difficult, do not worry! For now, you just need to remember the conversions shown in the table above.
The prefix rules are as follows:
The prefix "" stands for kilo, which means . Therefore,
The prefix "" stands for milli, which means . Therefore,
Notice that if we add to itself times, we get exactly Therefore, equals as stated in the table.
A melon has a mass of What is this mass in grams?
A table showing the metric units of mass is given below.
| Name | Symbol | Conversion |
|---|---|---|
| Kilogram | ||
| Gram | Base Unit | |
| Milligram |
So, is equivalent to
A weight in a school laboratory has a mass of $1\,\textrm{kg}.$ What is this mass in grams?
|
a
|
$0.1\,\textrm g$ |
|
b
|
$0.01\,\textrm g$ |
|
c
|
$10\,\textrm g$ |
|
d
|
$100\,\textrm g$ |
|
e
|
$1\,000\,\textrm g$ |
A peanut has a mass of $1\,\textrm{g}.$ What is this mass in milligrams?
|
a
|
$0.001 \, \textrm{mg}$ |
|
b
|
$10 \, \textrm{mg}$ |
|
c
|
$1\,000 \, \textrm{mg}$ |
|
d
|
$100 \, \textrm{mg}$ |
|
e
|
$0.01 \, \textrm{mg}$ |
Another way to measure mass is to use customary units. The most common customary units of mass are ounce, pound, and ton.
A table showing some of the most common customary mass units is shown below.
| Name | Symbol | Conversion |
|---|---|---|
| Ton | ||
| Pound | ||
| Ounce |
Let's give some examples of each unit, going from the largest unit to the smallest :
A small car could have a mass of around
A small bag of rice has a mass of around
A single slice of bread could have a mass of around
Customary units are not standard in the scientific community. However, they are commonly used in the United States and other countries.
Suppose we want to measure the mass of a flat-screen TV. Which of the following customary units could we use?
A table showing the customary units of mass is given below.
| Name | Symbol |
|---|---|
| Ton | |
| Pound | |
| Ounce |
Therefore, from the given options, the only unit of mass is
Suppose we want to measure the mass of a pencil. Which customary unit could we use?
|
a
|
$\textrm{yr}$ |
|
b
|
$\textrm{pint}$ |
|
c
|
$\textrm{oz}$ |
|
d
|
$\textrm{s}$ |
|
e
|
$\textrm{ft}$ |
Suppose we want to measure the mass of a soccer ball. Which customary unit could we use?
|
a
|
$\textrm{yd}$ |
|
b
|
$\textrm{s}$ |
|
c
|
$\textrm{in}$ |
|
d
|
$\textrm{pt}$ |
|
e
|
$\textrm{lb}$ |
An american bison has a mass of What is this mass in pounds?
A table showing the customary units of mass is given below.
| Name | Symbol | Conversion |
|---|---|---|
| Ton | ||
| Pound | ||
| Ounce |
So, is equivalent to
A book has a mass of $1\,\textrm{lb}.$ What is this mass in ounces?
|
a
|
$10\,\textrm{oz}$ |
|
b
|
$3\,\textrm{oz}$ |
|
c
|
$8\,\textrm{oz}$ |
|
d
|
$2\,\textrm{oz}$ |
|
e
|
$16\,\textrm{oz}$ |
A giraffe has a mass of $1\,\textrm{ton}.$ What is this mass in pounds?
|
a
|
$ 1,600\,\textrm{lb}$ |
|
b
|
$10,000\,\textrm{lb}$ |
|
c
|
$ 2,000\,\textrm{lb}$ |
|
d
|
$4,000\,\textrm{lb}$ |
|
e
|
$ 1,000\,\textrm{lb}$ |