Metric System Podcast
For Chemistry
Metric System
• In order to do well in Chemistry this year,
you must be familiar with basic metric
system units and prefixes.
• You must also be able to perform simple
conversions.
• And you should have an idea of how the
metric units compare to the everyday units
used in the United States.
Length
• The basic unit for length in the metric
system is the meter.
• A meter is 39.37 inches, or a bit more than
a yard. It is a useful unit for measuring the
length of objects such as rooms, boats,
houses, playing fields, etc.
• The symbol for meter is m.
Length
•
If you wish to measure larger or smaller things, it may be more convenient
to use a prefixed unit of length.
•
For large distances, like between two towns, the kilometer is used. A
kilometer is 1000 meters. Kilo comes from the Greek word for thousand.
The symbol for kilometer is km. A kilometer is a bit more than a half mile.
•
For small objects, you might use centimeters or millimeters. A centimeter is
1/100th of a meter. Centi comes from the Latin word for hundred. The
symbol for centimeter is cm. A millimeter is 1/1000th of a meter. Milli
comes from the Latin word for thousand. The symbol for millimeter is mm.
There are 2.54 cm in an inch.
•
For very small objects, such as atoms or molecules, you might use
nanometers. A nanometer is 1/1000000000th (billionth) of a meter. Nano
comes from the Greek word for dwarf. The symbol for nanometer is nm. A
nanometer is too small to picture.
Length
1 kilometer (km) = 1000 meters (m)
1 meter (m) = 100 centimeters (cm)
1 meter (m) = 1000 millimeters (mm)
1 meter (m) = 109 nanometers (nm)
Volume
• The basic unit for volume in the metric system is
the liter. A liter is 33.8 ounces, or a little more
than a quart. It is a useful unit for measuring the
volume of drinks or gasoline or other fluids. The
symbol for liter is L.
• For measuring smaller volumes the milliliter is
convenient.
• A milliliter is 1/1000th of a liter.
• The symbol for milliliter is mL.
• A cc or cubic centimeter is equal to a milliliter.
Volume
1 Liter (L) = 1000 milliliters (mL)
1 milliliter (mL) = 1 cubic centimeter (cm3) or (cc)
Mass
• The basic unit for mass in the metric system is the gram.
• A gram is .0353 ounces, or the mass of 1 mL of water.
• It is a useful unit for measuring the mass of recipe ingredients and
quantities of food. A candy bar is about 30 grams. The symbol for
gram is g.
• For measuring larger objects the kilogram is convenient. A kilogram
is 1000 grams. It is also about 2.2 pounds mass. The symbol for
kilogram is kg.
• For measuring smaller objects the milligram is used. A milligram is
1/1000th of a gram. Medicines are often measured in milligrams.
The symbol for milligram is mg.
Mass
1 kilogram (kg) = 1000 grams (g)
1 gram (g) = 1000 miligrams (mg)
*Also know that 1 g of water has a volume of 1 mL or 1 cm3
Notice that this fact links the metric units for length, volume and mass
Metric Prefixes
• Must Know
– kilo
1 kx = 1000x
– centi
100 cx = 1x
– milli
1000 mx = 1x
– nano
109 nx = 1x
*x = m or L or g
• For Reference
– Tera
1 Tx = 1012 x
– Giga
1 Gx = 109 x
– Mega
1 Mx = 106 x
– deci
10 dx = 1x
– micro
106 mx = 1x
– pico
1012 px = 1x
Conversions
• Conversions can be done easily utilizing
the following steps:
1. Identify given quantity and units.
2. Identify desired units.
3. Make ratio of desired units to given units (desired/given)
4. Make equation as follows:
_______desired units = given units X ratio of desired units/given units
5. Solve.
Conversions
Example- How many milligrams are in 8.13 grams?
1. Given2. Desired3. Ratio-
4.
5. Solve!
Conversions
Sometimes, two ratios are necessary.
Example- How many kilometers are there in 85,412
centimeters?
1. Given-
2. Desired3. Ratios4.
5. Solve!
Conversions
Here are some more practice conversions.
1. How many liters are in 23,472 ml?
2. How many mg are in 32.1 kg?
3. How many nm are in .5 km?