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Matter and Measurement
• matter is hierarchical (of
increasing dimension,
complexity, etc.)
• elements are the
chemical fundmental units
sodium, Na, & chlorine, Cl2
• compounds are
combinations of
elements
sodium chloride,
NaCl
• molecules
• ionic compounds
water, H2O
• nucleus
– protons
– neutrons
• electrons
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Na: 11 protons, 11 electrons
Cl: 17 protons, 17 electrons
Na+
Cl-
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States of matter ↔ Energy of particles ↔ Interactions between particles
the physical state of a substance depends on the conditions:
temperature
pressure
electric field strength
etc.
and on the substance:
composition
mixture vs. compound
CD-ROM screen 1.9
the state is usually called the phase, such as “the liquid phase”
kinetic (motion) energy of particles
increases with increasing temperature T
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1
10-2 m
10-3 m
Copper ore
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Copper ore grains
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10-5 m
10-10 m
Copper ore grains, higher resolution
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Copper atom clumps on silicon surface
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2
single cell
cm mm
0.2 m
10-3
µm
10-6
10-12 m
CD-ROM screen 1.4
2m
Copper atom, theory
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Physical properties
(1 Å = 10-10 m)
single cell
µm
Each arrow represents a
decrease to 1/10th scale.
molecules
atoms
nm
10-9
pm
10-12
•usual definition
•color
•gas, liquid, solid
•state
•melting point
•T at which solid ↔ liquid
•boiling point
•T at which liquid ↔ gas
•heat of vaporization •heat needed to convert liquid → gas
•heat of fusion
•heat needed to convert solid → liquid
•mass per unit volume (g/L)
•density
•amount of substance that can
•solubility
dissolve per unit volume
Each arrow represents a
decrease to 1/10th scale.
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Problem:
A piece of copper has a mass of
57.54 g. It is 9.36 cm long, 7.23 cm wide, and
0.95 mm thick. Calculate density (g/cm3).
Density =
mass (g)
volume (cm 3 )
SOLUTION
1. Get dimensions in common units.
1cm
= 0.095 cm
10 mm
2. Calculate volume in cubic centimeters.
0.95 mm •
(9.36 cm)(7.23 cm)(0.095 cm) = 6.4 cm3
3.
Calculate the density.
57.54 g
= 9.0 g / cm 3
6.4 cm 3
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Relative Densities of the Elements
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•Be sure to notice that
DENSITY is an INTENSIVE
PROPERTY of matter.
•INTENSIVE — does not
depend on quantity of
matter. Examples are
density and temperature.
•Contrast with EXTENSIVE
— depends on quantity of
matter. Examples are mass
and volume.
•Subdividing matter does
not change intensive
properties, it does change
extensive properties.
Styrofoam
Brick
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Chemical Properties and Chemical
Change
•Burning hydrogen (H2) in
oxygen (O2) gives H2O.
• Chemical change or chemical
reaction involves the transformation of one or more atoms
or molecules into one or more
different molecules.
• Physical change involves the
change in state or shape of a
substance while preserving its
chemical identity.
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UNITS OF MEASUREMENT
Use SI units — based on the metric system
length
(meter, m)
mass
(kilogram, kg,
and gram, g)
time
(second)
temperature
(Kelvin, K)
Volume in liters (L) → conversion to cm3:
1 cm3 = 1 mL
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Temperature
Scales
PROBLEM:
PROBLEM: Mercury
Mercury (Hg)
(Hg) has
has aa density
density
33. What is the mass of 95 mL
of
13.6
g/cm
of 13.6 g/cm . What is the mass of 95 mL
of
of Hg?
Hg? In
In grams?
grams? In
In pounds?
pounds?
100 oF
38 oC
311 K
oF
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oC
K
5

TK = T°C + 27315
. =  (T° F + 495.67)
9

5

T°C = TK − 27315
. =  (T° F − 32 )
9

9
9
T° F = {T°C } + 32 = {TK } − 459.67
5
5
Solve the problem using DIMENSIONAL
(OR UNIT) ANALYSIS.
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First, note that
Significant figures
(Significant digits)
1 cm3 = 1 mL
Then, use dimensional analysis to
calculate mass.
13.6 g
95 cm 3 •
cm 3
= 1.3 x 10 3 g
What is the mass in pounds? (1 lb = 454 g)
1.3 x 10 3 g •
1 lb
454 g
= 2.8 lb
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Rule: The last digit (on the right) is uncertain to ± 1.
Rule: Leading zeros don’t count.
Rule: Trailing zeros don’t count if there is no
decimal point.
0.120
0.08003
200
200.0
3 SF
4 SF
1 SF
4 SF
Note: Some numbers are
exact, such as π = 3.14159…,
and have an infinite # of SF
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Some algebra with sig figs
Algebra and significant figures
Multiplication and division: final answer has the same #
of SF as the least significant
number used to produce it.
Addition and subtraction: final answer has the same #
of digits to the right of the
decimal point as the number
with the least # of digits to the
right.
56.49 + 3.3 = 59.79
59.8
1 right of dec pt
4 SF, 2 right of dec pt
2 SF, 1 right of dec pt
56.49 × 3.3 = 186.417
190
2 SF
56.49 × π = 177.468569
177.5
4 SF
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