1. CHEMISTRY 161
Chapter 3
Measurements

2. Measurements measurements are numerical (quantitative) observations
how much?
weight; volume; speed; energy; density; distance
qualitative observations
what?
color, small

3. Measurements
number
error*
unit
*uncertainty

4. SI base unit measurement unit symbol length meter m mass gram g
time second s
electrical current ampere A
temperature Kelvin K
amount of substance mole mol
luminous intensity candela cd
all units are derived from 7 SI base units

5. derived units area length  width length  width  height volume
distance / time
velocity
velocity / time
acceleration
Force [N]
acceleration  mass
force / area
Pressure [Pa; mbar, torr]

6. Measurements
number
unit 50
m s-1
m s-1
300,000,000

8. Decimal Multipliers prefix symbol factor power of 10
mega M
kilo k
deci d
centi c
milli m
1000 g
0.01 g
0.001 g

9. Conversion Measurement English to Metric Metric to English
Length 1 ‘’ = 2.54 cm m = in.
1 yd = m 1 km = mile
1 mile = km
Mass 1 lb = g 1 kg = lb
1 oz = g
Volume 1 gal = L 1 L = qt
1 pt = mL
1 oz (fluid) = 29.6 mL
1 L = 1000 mL = 1000 cm3

10. Temperature
0 K
-273 OC

11. NASA-Mars Polar Lander

12. number unit error Measurements measuring device inaccurate reading
multiple measurements
average (statistics)

13. Significant Digits T = 24.3 ºC (3 significant digits)
0.034 K
3.4  10-2 K
3.40  10-2
combining significant digits

14. Summary SI units and conversion of units 2. error
3. number of significant digits