Biology I Lab instructions: Metric System

1. Metric System

2. First measurements
• Based on the human body
Example: foot, hand
• Standards evolved but not constant
• Lack of common units a problem

3. Solution
• 1791 French Academy of Sciences
devised metric system
– Metric means measure in French
– Based on unit of 10
• Easy to make conversions between units
– Widely adapted
• 1960 renamed International System of
Units (SI)

4. Metric Units
Unit Metric measure Abbreviation
Length Meter m
Volume Liter L
Mass Gram g
Temperature Celcius C

5. Metric prefixes we’ll use
Prefix Symbol Multiplier Notation
nano n 0.000000001 10-9
micro µ 0.000001 10-6
milli m 0.001 10-3
centi c 0.01 10-2
Base unit g, m, L 1 100
kilo k 1000 103

6. Metric System
• An easy way to move within the metric system is
by moving the decimal point one place for each
“step” desired
Example: change meters to centimeters
1 meter = 10 decimeters = 100 centimeters
or
1.00 meter = 10.0 decimeters = 100. centimeters
kilo hecto deca
meter
liter
gram
deci centi milli

7. Metric System
• If you move to the left in the diagram, move
the decimal to the left
• If you move to the right in the diagram,
move the decimal to the right
kilo hecto deca
meter
liter
gram
deci centi milli

8. Metric conversion examples
15.2 millimeters = _________________ meters
13 centigrams= __________________ micrograms
9.74 liters = __________________ milliliters
8051 nanometers = ______________ micrometers

9. Scientific Notation
• You can work backwards from scientific
notation
– The number in the superscript position of the
10 tells you how many places to move the
decimal and in what direction
1 x 103
= 1000
4.7 x 105
= 470000
3.2 x 10-3
= 0.0032

10. Length: Meter (cm, mm)
• Based on the physical
measure on the earth
– Length from the North
Pole to the Equator
divided into 10 million
parts
• Measure with a ruler
or tape measurer

11. Mass/Weight: Grams (mg)
• The quantity of matter
in a material
• Gram is typical unit
used in the laboratory
• Measure with scale or
balance

12. Volume: Liter (ml)
• Space occupied
by a unit
– 3 dimensional
• Units are cubed
• ml=cm3
• Typically used to
measure liquids
• Meniscus:
curvature of water

13. Micropipette
• Tool used to
pipette small
volumes of liquids
• Measure in
microliters (10-6
)
• Will use this tool
again later in the
semester

14. Temperature: Celsius (C°)
• Measure of concentration of heat
• The average amount of motion per
molecule
0°C=freezing point of H2O
100°C=boiling point of H2O
To convert:
F to C: C = ( F - 32) / 1.8
C to F: F = C × 1.8 + 32