In Science and Medicine, We
use the Metric System!
Dimensions
• Unit of length: meter
• Unit of mass: gram
• Unit of volume: liter
SI Base Units of Measurement
• Mass = the gram; g
• 1 gram ≈ 1/28 ounce
• Length = the meter; m
• 1 meter ≈ 1.094 yard
• Volume = the liter; l
• defined as 1000 cubic centimeters
• 1 liter ≈ 1.057 quart
• Temperature = degrees Celsius; oC
Prefixes
• The metric system uses prefixes to
represent units
• smaller and larger than the
fundamental unit by factors of 10.
• For example, a centimeter is 1/100 of a meter,
and a kilometer is 1000 times a meter
• For very large numbers, we use the powersof-ten notation, e.g. 102 = 100, 106 =
1,000,000, 10-2 = 0.01
Prefixes
• One of the clever ideas behind the system was to use only
multiples of ten.
Converting Between Metric Units
• To convert from a LARGER unit of measure to a
SMALLER unit of measure, MULTIPLY by the
“order-of-magnitude difference” between the units.
• Example: 1.2 mg = ______ g
• 1 mg = 1000 g
• 1.2 mg = 1.2 x 1000 g = 1200 g
• Remember to check if your answer is logical.
• It should take a GREATER NUMBER of SMALL
UNITS to equate to a LESSER NUMBER of LARGE
UNITS.
• A microgram is smaller than a milligram (by a
factor of 1000), so a given number of milligrams
should be equal to many more micrograms (1000
times as many).
Converting Between Metric Units
• To convert from a SMALLER unit of measure to a
LARGER unit of measure, DIVIDE by the “order-ofmagnitude difference” between the units.
• Example: 250 ml = ______ l
• 1 l = 1000 ml
• 250 ml = 250 ÷ 1000 l = 0.25 l
• Is your answer is logical?
• It should take a LESSER NUMBER of LARGE
UNITS to equate to a GREATER NUMBER of
SMALL UNITS.
• A liter is larger than a milliliter (by a factor of 1000), so a
given number of milliliters should be equal to fewer liters
(1/1000 as many).
Thinking in Metric Units of Length
•
1 kilometer = ~0.62 or ~5/8 mi
• 1 meter = 1.09 yard = 39.4 in
• 1 centimeter = ~4/10 inch
• 1 angstrom = 1/10 nm or 10-10m
•
1 mile = ~1.6 km
• 1 yard = ~0.91 m
• 1 foot ~30.5 cm
• 1 inch = ~2.54 cm
Thinking in Metric Units of Volume
•
1 liter = ~1.06 quart
• 1 milliliter = 1 cubic cm (1cc)
•
•
•
~"a thimble full"
•
Examples
•
•
•
•
1 teaspoon ≈ 5ml
12 oz. soda ≈ 360 ml
2-liter bottle of soda
•
1 gallon = ~3.8 l
1 quart = ~0.95 l
1 pint = ~0.47 l
1 cup = ~240 ml
1 fluid oz. ~30 ml
2 liters~1/2 gal.
Thinking in Metric Units of Mass
• 1 kilogram = 2.2 pounds
• 1 pound = 454 g
• 1 gram = ~"a thimble
• 1 ounce = ~28 g
full" of water
• Examples
•
70 kg human = 154 lbs.
• 1 ml of water weighs ~1 g
Estimate
• The length of:
• your bare foot
• your driveway
• The volume of:
• a coffee cup
• a bottle of shampoo
• The mass of:
• a steak
• a dog
Celsius: The Metric Temperature Scale
• Also called the centigrade scale.
• Definitions
100C
212F
0C
32F
• 0 Celsius = 32 Fahrenheit = water freezes
• 100 Celsius = 212 Fahrenheit = water
boils
• Therefore, 1C = 1.8F
• Conversions
•  Celsius = 5/9 x ( Fahrenheit - 32)
•  Fahrenheit = (9/5 x  Celsius) + 32
Thinking in Celsius
• -10 Celsius = frigid (14 F)
• 0 Celsius = cold (32 F)
• 10 Celsius = cool (50 F)
• 20 Celsius = comfortably warm (68 F)
• 30 Celsius = hot (86 F)
• 40 Celsius = very hot (104 F)
• What would you wear outside in tempsf:
• 10C, 0C, 10C, 20C, 30C?