Chapter 5, Part 3
Measurements and Calculations
5.6 Dimensional Analysis
1 in. = 2.54 cm is an equivalence statement
and can be turned into a conversion factor:
1 in./2.54 cm or
2.54 cm/1 in.
Any equivalence statement can be used in this
manner.
Example: 62 cm = ? In.
62 cm x 1 in./2.54 cm = 24 in. (note sig figs)
Example: 26.2 mi. = ? Km.
26.2 mi. X 1760 yd/1 mi. X 1 m/1.094 yd x
1 km/103 m = 42.1 km
Embedded problem: (convert the speed of light
from 3.00 x 108 meters per second to miles
per hour.)
5.7 Temperature Conversions
Fahrenheit
Celsius
Kelvin
b.p. water
212
100
373
f.p. water
32
0
273
Absolute zero
-460
-273
0
(note: no degree symbol “o” is used in the Kelvin
scale. It is an absolute scale.)
Conversions: Celsius to Kelvin: add 273 to Celsius
Figure 5.6: The three major temperature scales.
Figure 5.7:
Converting
70 degrees
Celsius to
Kelvin
units.
Figure 5.8: Comparison of the Celsius
and Fahrenheit scales.
Example: 70.oC = ? K
70.oC + 273 = 343 K
Example: 77 K = ? oC
77 K - 273 = -196oC
Problem: Which temperature is colder, 172 K or
-75 oC? (172 K)(Why?)
5.8 Density- amount of matter present in a given
volume of a substance.
Density = mass/volume
Mass = density x volume
Volume = Mass/Density
Specific gravity- ratio of the density of a given liquid
to the density of water @ 4oC (has no unit)
Example: 23.50 mL of a certain liquid has a mass of
35.062 g. Calculate density.
D = M/V = 35.062 g/23.50 mL = 1.492 g/mL
Problem: 35.8 mL of a cleaner has a mass of 28.1 g.
Which of the four substances in the table on p.
144 is the major component?
D = M/V = 28.1 g/35.8 mL = 0.785 g/mL
Therefore, isopropyl alcohol.
Example: V = M/D = 225 g/13.6 g/mL =
16.5 mL