Transcript III. Unit Conversions

A. Number vs. Quantity
• Quantity - number + unit
UNITS MATTER!!
Metrics – Base Units
Measureme
nt
Base Unit
Abbreviatio
n
Length
meter
m
Mass
gram*
g
Volume
liter
L
Temperature
Celcius*
(centigrade*)
or
Kelvin
oC
or
K
*These are not SI units, but are base units for these measurements.
Base units continued
Amount of
Substance
mole
mol
Time
seconds
s
A. SI Prefix Conversions
Prefix
mega-
Symbol
M
Factor
106
k
103
BASE UNIT
---
100
deci-
d
10-1
Meter (m)
centi-
c
10-2
seconds(s)
milli-
m
10-3
micro-

10-6
nano-
n
10-9
pico-
p
10-12
move right
move left
kilo-
Base Units
Gram (g)
Liter (L)
Metrics
Why use the metric system?
Metrics
• Because of the worldwide use of science, an
international system of measurements was developed
in 1960.
– This system is referred to as the SI (le Systeme
International).
• This system utilizes specific SI base units.
• The advantage of the system is that it is a decimal
system based on multiples of 10.
• The system uses prefixes to indicate the multiples
of 10. (How many times you move the decimal.)
A. SI Prefix Conversions
532 m
NUMBER
UNIT
0.532 km
= _______
=
NUMBER
UNIT
A. SI Prefix Conversions
1. Find the difference between the exponents of
the two prefixes.
2. Move the decimal that many places.
To the left
or right?
(exponent of start)-(exponent of end)
• 33 kg to mg
– Kilo has an exponent of 3 and milli has an
exponent of -3
(3) – (-3) = 6 since it is positive, you move it places
to the right
• 24 mm to m
– Milli has an exponent of -3 and meter is a base
unit so it has an exponent of 0
(-3) – (0) = -3 since it is negative you move 3 places
to the left
A. SI Prefix Conversions
1) 20 cm =
______________ m
2) 0.032 L =
______________ mL
3) 45 m =
______________ nm
4) 805 dm =
______________ km
Temperature Scales
• Fahrenheit: Based upon the boiling and
melting points of alcohol.
• Celsius: Based upon the boiling and melting
points of water.
– 0o C = Melting Point
– 100o C = Boiling Point
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Compare Temperatures
F = C (1.8) + 32
C = F – 32 (.555)
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Absolute Temperature
• Kelvin: Based scale upon absolute zero.
– Absolute Zero: The coldest temperature possible.
(Theoretical Point)
• Remember that temperature is based on average KE.
Therefore, at 0 Kelvin there will be absolutely no
movement of the atoms/molecules of the substance.
– Absolute Zero = -273.16 C
– Used the same sized graduations as in the Celsius
scale.
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Kevin to Celsius Comparisons
•Kelvin degrees are
the same graduation
as Celsius
273.16 K
Melting Point
0C
•They simply start (0)
at different places.
•Celsius at Melting Point,
Kelvin at Absolute Zero
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0K
Absolute Zero
-273.16 C
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Kelvin/Celsius Conversions
•K = C + 273*
•C = K – 273*
*A more precise
value would be
273.16, but to keep
it simple, we’ll use
the 273 value.
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273.16 K
0K
Melting Point
Absolute Zero
0C
-273.16 C
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