Transcript Slide 1

CHEMISTRY 161
Chapter 3
Measurements
Measurements
measurements are numerical (quantitative) observations
how much?
weight; volume; speed; energy; density; distance
qualitative observations
what?
color, small
Measurements
number error*
*uncertainty
unit
SI base unit
measurement
length
mass
time
electrical current
temperature
amount of substance
luminous intensity
unit
meter
gram
second
ampere
Kelvin
mole
candela
symbol
m
g
s
A
K
mol
cd
all units are derived from 7 SI base units
derived units
area
length  width
volume
length  width  height
velocity
distance / time
acceleration
velocity / time
Force [N]
Pressure [Pa; mbar, torr]
acceleration  mass
force / area
Measurements
number
unit
50
m s-1
300,000,000
m s-1
Decimal Multipliers
prefix symbol factor power of 10
mega
M
1000000
106
kilo
k
1000
103
deci
d
0.1
10-1
centi
c
0.01
10-2
milli
m
0.001
10-3
1000 g
0.01 g
0.001 g
Conversion
Measurement English to Metric
Metric to English
Length
1 ‘’ = 2.54 cm
1 m = 39.37 in.
1 yd = 0.9144 m
1 km = 0.6215 mile
1 mile = 1.609 km
Mass
1 lb = 453.6 g
1 kg = 2.205 lb
1 oz = 28.35 g
Volume
1 gal = 3.785 L
1 L = 1.057 qt
1 pt = 946.4 mL
1 oz (fluid) = 29.6 mL
1 L = 1000 mL = 1000 cm3
Temperature
0K
-273 OC
NASA-Mars Polar Lander
Measurements
number
error
unit
measuring device
inaccurate reading
multiple measurements
average (statistics)
Significant Digits
T = 24.3 ºC (3 significant digits)
T = 24.32 ºC (4 significant digits)
0.034 K
3.4  10-2
0.0340 K
3.40  10-2
combining significant digits
Summary
1.SI units and conversion of units
2. error
3. number of significant digits