Chemistry: SI Units

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Chemistry SI Units Conversions
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SI Base Units of Measurecommonly used in
chemistry

• Time second (s)
• Length,distance meter (m)
• Mass kilogram (kg)
• In class, we consider the base unit to be
  grams.
• Volume liter (l)
• Temperature Kelvins (K) note no degree symbol
• In chemistry lab, we use the Celsius temperature
  scale. ( C)

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Derived Units

• A derived unit is one in which the units are
  combined mathematically.
• Volume cubic centimeter (cm3)
• (cm x cm x cm)
• Area square meter (m2)
• ( m x m)
• Density mass ? volume

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Converting Celsius to Kelvin
Kelvins ?C 273
C Kelvins - 273
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Prefixes for SI Units

• Prefixes for units smaller than 1
• micro (?) 1 X 10-6 or
• milli (m) 1 X 10-3 or
• centi (c) 1 X 10-2 or
• deci (d) 1 X 10-1 or
• Prefixes for units larger than 1
• kilo (k) 1 X 103 or 1,000

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Conversion Using the Factor-Labeling Method
(Dimensional Analysis)
Starting unit
Target unit
Problem Convert 32.05 cm to m

X
Step 1 write down the starting measurement
number and unit!
Step 2 Convert from this prefix to the base
unit. (This means meters, liters or grams.)
Step 5 If you have arrived at the target unit,
you are done! Be sure to include the unit and
significant figures in your answer!
Step 3 Cancel the units that divide each other
out.
Step 4 Perform the math divide by the numbers
on the bottom, multiply by the numbers on the top!
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Practice!
Convert 0.00450 km to cm
?
X
X

The correct answer is 450 cm, but thats only 2
sig figs. ?????
Use scientific notation to correct the sig figs!
4.50 x 102 cm