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# Chemistry

Base Units

Following are seven base units used in the metric system:

Table 1: Base Units

 Property Unit Symbol Amount of substance mole mol Electric current ampere amp Length meter m Luminous intensity candela cd Mass kilogram kg Temperature kelvin K Time second s

Metric-Metric Conversions

Conversion factors for the metric system can be determined from prefixes added to -meter. Some of the common prefixes are given below.

Table 2: Prefixes for the Metric System

Prefix Symbol Factor
femto- f 10-15
pico- p 10-12
nano- n 10-9
micro- µ 10-6
milli- m 10-3
centi- c 10-2
deci- d 10-1
Base unit   100
deca- D 101
hecto- h 102
kilo- k 103
mega- M 106
giga- G 109

• Every time you move to the left, move the decimal point to the right the same amount of times, or divide the value by the negative powers of ten. Power in this case is equal to the number of times you moved.
• Every time you move to the right, move the decimal point to the left however many times you moved, or divide the value by the positive powers of ten. Power in this case is equal to the number of times you moved.

Example I

Convert 12.52 L to mL

To go from L to mL, you have to move three times to the left. Therefore, move the decimal three times to the right.

Method 1

Moving the decimal three places to the right gives: Method 2

SInce you moved three spaces to the left to get to ml on the diagram divide the value by ten to the power of minus three  (10-3). Have questions about how the ten to the power of three became positive? Check out this guide for more details.

Converting Units Using Conversion Factor

 Units of length in the metric system Units of weight in the metric system Units of volume in the metric system 1,000 millimeters (mm) = 1 meter 100 centimeters (cm) = 1 meter 10 decimeters (dm) = 1 meter 1 dekameter (dam) = 10 meters 1 hectometer (hm) = 100 meters 1 kilometer (km) = 1000 meters 1 gram = 1,000 milligrams (mg) 1 gram = 100 centigrams (cg) 1 kilogram (kg) = 1,000 grams 1 metric ton (t) = 1,000 kilograms 1 cc = 1 cm3 1 milliliter (mL) = 1 cm3 1 liter (L) = 1,000 millimeters (mL) 1 hectoliter (hL) = 100 liters (L) 1 kiloliter (kL) = 1,000 liters (L)

Example 1

Convert 42.50 m to km

Step 1 : Write the conversion factor from the table above.

1 kilometer (km) = 1000 meters (m)

Step 2 : Write the conversion factor as a ratio.

Since we are converting meters to kilometers, write the km on the top and m on the bottom, as shown below: Step 3: Multiply 42.50m by the above ratio. Then the answer becomes 0.04250 km with four significant digits.

** Notice how the "m" on the top and the "m" at the bottom cancel out to give "km" as the final unit, as seen below: Study tips for unit conversion

• Pick the method that you are most comfortable with and always use it.
• If you choose to use the conversion factor method, memorize the most important ones used in your courses.
• If you choose to use a conversion diagram, make sure to know the prefixes and the factors and where they are placed in your diagram.
• Memorization technique: write down the information or make a chart on a big piece of paper and post it somewhere in your room where you can see it often. Every time you get a chance, even if it's a few minutes, read through and review as many as you can.

Want to check your understanding? Try our online Quiz!