Chemistry:
The Study of Change
Chapter 1
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Chemistry: A Science for the 21st Century
• Health and Medicine
• Sanitation systems
• Surgery with anesthesia
• Vaccines and antibiotics
• Gene therapy
•Energy and the Environment
• Fossil fuels
• Solar energy
• Nuclear energy
2
Chemistry: A Science for the 21st Century
• Materials and Technology
• Polymers, ceramics, liquid crystals
• Room-temperature superconductors?
• Molecular computing?
• Food and Agriculture
• Genetically modified crops
• “Natural” pesticides
• Specialized fertilizers
3
The Study of Chemistry
Macroscopic
Microscopic
4
Qualitative data consists of general
observations about the system
The coffee is hot
The boy is tall
Quantitative data comprises numbers
obtained by various measurements of the
system.
The coffee is heated to 97°C
John is 5 ft 6 in tall
5
The scientific method is a systematic
approach to research
A hypothesis is a tentative explanation for a
set of observations
tested
modified
6
A law is a concise statement of a relationship
between phenomena that is always the same
under the same conditions.
Force = mass x acceleration
A theory is a unifying principle that explains
a body of facts and/or those laws that are
based on them.
Atomic Theory
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Problem 1.3
Classify the following statement as
(a) qualitative
(b) quantitative
1.The sun is approximately 93 million miles
from earth.
2. Leonardo daVinci was a better painter than
Michelangelo.
3.Ice is less dense than water.
4.Butter tastes better than margarine.
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Problem 1.4 (a)
Classify the following statement as a
(a) hypothesis (b) law (c) theory
1.Beethoven’s contribution to music would have
been much greater if he had married.
2. An autumn leaf gravitates toward the ground
because there is an attractive force between the
leaf and the earth.
3. All matter is composed of very small particles
called atoms
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Chemistry is the study of matter and the
changes it undergoes
Matter is anything that occupies space and
has mass.
A substance is a form of matter that has a
definite composition and distinct properties.
liquid nitrogen
gold ingots
silicon crystals
10
A mixture is a combination of two or more substances
in which the substances retain their distinct identities.
1. Homogenous mixture – composition of the
mixture is the same throughout.
clear juice (apple, cranberry), bronze, solder
2. Heterogeneous mixture – composition is not
uniform throughout.
cement,
iron filings in sand
11
Physical means can be used to separate a mixture
into its pure components.
magnet
distillation
12
A compound is a substance composed of atoms
of two or more elements chemically united in fixed
proportions.
Compounds can only be separated into their
pure components (elements) by chemical
means.
lithium fluoride
quartz
dry ice – carbon dioxide
13
An element is a substance that cannot be
separated into simpler substances by chemical
means.
• 114 elements have been identified
• 82 elements occur naturally on Earth
Element 118
discovered
in 2006!
gold, aluminum, lead, oxygen, carbon, sulfur
• 32 elements have been created by scientists
technetium, americium, seaborgium
14
15
Classifications of Matter
16
Problem 1.16(a)
Classify the following as a(n)
(a) element
(c) homogeneous mixture
(b) compound (d) heterogeneous mixture
filtered sea water
Helium gas
Kosher salt (sodium chloride)
A bottle of soda (capped, unshaken)
A milkshake
Filtered air in a bottle
concrete
17
A Comparison: The Three States of Matter
18
The Three States of Matter: Effect of a Hot
Poker on a Block of Ice
gas
liquid
solid
19
Types of Changes
A physical change does not alter the composition
or identity of a substance.
sugar dissolving
ice melting
in water
A chemical change alters the composition or
identity of the substance(s) involved.
hydrogen burns in
air to form water
20
Problem 1.12(a)
Does the following describe a (a) chemical change
or a (b) physical change?
1. The helium gas inside of a balloon tends to leak
out after a few hours.
2. Frozen orange juice is reconstituted by adding
water to it.
3. The growth of plants depends on the sun’s
energy in a process called photosynthesis.
4. A spoonful of table salt dissolves in a bowl of
soup.
21
Extensive and Intensive Properties
An extensive property of a material depends upon
how much matter is is being considered.
• mass
• length
• volume
An intensive property of a material does not
depend upon how much matter is is being
considered.
• density
• temperature
• color
22
Matter - anything that occupies space and has mass.
mass – measure of the quantity of matter
SI unit of mass is the kilogram (kg)
1 kg = 1000 g = 1 x 103 g
weight – force that gravity exerts on an object
W=mxa
SI unit of force is the Newton (N)
1 N = 1 kg∙m/s2
Interestingly, the process of measuring mass is called
weighing!
23
Mass is constant, while weight is dependent on
location
On the moon, a = 1.67 m/s2
W = m x a = 1 kg x 1.67 m/s2
1.67 Newton
On earth, a = 9.81 m/s2
W = 1 kg x 9.81 m/s2 = 9.81 kg∙m/s2
9.81 Newton
9.81 Newton/1.67 Newton = 5.87
A 1 kg mass weighs almost 6 times more on earth than on
the moon!
24
International System of Units (SI)
25
26
Volume – SI derived unit for volume is cubic meter (m3)
1 cm3 = (1 x 10-2 m)3 = 1 x 10-6 m3
1 dm3 = (1 x 10-1 m)3 = 1 x 10-3 m3
1 L = 1000 mL = 1000 cm3 = 1 dm3
1 mL = 1 cm3
27
Density – SI derived unit for density is kg/m3
1 g/cm3 = 1 g/mL = 1000 kg/m3
mass
density =
volume
m
d= V
A piece of platinum metal with a density of 21.5
g/cm3 has a volume of 4.49 cm3. What is its mass?
28
Problem 1.22
The density of ethanol, a colorless liquid
that is commonly known as grain alcohol,
is 0.798 g/mL. Calculate the mass of 17.4
mL of the liquid.
29
30
A Comparison of Temperature Scales
K=
( 0C
+
273.15 0C)
1K
1 0C
273 K = 0 0C
373 K = 100 0C
0F
9
0F =
0C + 32 0F
x
0
5 C
32 0F = 0 0C
212 0F = 100 0C
31
Convert 327.5 0C to degrees Fahrenheit.
Convert 172.9 0F to degrees Celsius.
Convert 77 K, the boiling point of liquid nitrogen to
degrees Celsius.
32
Problem 1.24(a)
Normally the human body can endure a
temperature of 105 °F for only short
periods of time without permanent
damage to the brain and other vital
organs. What is the temperature in °C?
33
Problem 1.24(b)
Ethylene glycol is a liquid organic
compound that is used as an antifreeze in
car radiators. It freezes at -11.5 °C.
Calculate the freezing point in °F.
34
Problem 1.24(c)
The temperature of the surface of the sun
is about 6300 °C. What is this
temperature is °F?
35
Problem 1.24(d)
The ignition temperature of paper is 451
°F. What is the temperature in K?
36
Scientific Notation
The number of atoms in 12 g of carbon:
602,200,000,000,000,000,000,000
6.022 x 1023
The mass of a single carbon atom in grams:
0.0000000000000000000000199
1.99 x 10-23
N x 10n
N is a number
between 1 and 10
n is a positive or
negative integer
37
Scientific Notation
568.762
0.00000772
move decimal left
move decimal right
n>0
n<0
568.762 = 5.68762 x 102
0.00000772 = 7.72 x 10-6
Addition or Subtraction
1. Write each quantity with
the same exponent n
2. Combine N1 and N2
3. The exponent, n, remains
the same
4.31 x 104 + 3.9 x 103 =
4.31 x 104 + 0.39 x 104 =
4.70 x 104
38
Scientific Notation
Multiplication
1. Multiply N1 and N2
2. Add exponents n1 and n2
Division
1. Divide N1 and N2
2. Subtract exponents n1 and n2
(4.0 x 10-5) x (7.0 x 103) =
(4.0 x 7.0) x (10-5+3) =
28 x 10-2 =
2.8 x 10-1
8.5 x 104 ÷ (5.0 x 109)=
(8.5 ÷ 5.0) x 104-9 =
1.7 x 10-5
39
Significant Figures
• Any digit that is not zero is significant
1.234 kg
4 significant figures
• Zeros between nonzero digits are significant
606 m
3 significant figures
• Zeros to the left of the first nonzero digit are not significant
0.08 L
1 significant figure
• If a number is greater than 1, then all zeros to the right of the
decimal point are significant
2.0 mg
2 significant figures
• If a number is less than 1, then only the zeros that are at the
end and in the middle of the number are significant
0.00420 g
3 significant figures
40
How many significant figures are in
each of the following measurements?
24 mL
3001 g
0.0320 m3
6.4 x 104 molecules
560 kg
41
Problem 1.34
How many significant figures are in each
of the following measurements?
a) 0.006 L
b) 0.0605 dm
c) 60.5 mg
d) 605.5 cm2
e) 960 x 10-3 g
f) 6 kg
g) 60 m
42
Significant Figures
Addition or Subtraction
The answer cannot have more digits to the right of the decimal
point than any of the original numbers.
89.332
+1.1
90.432
3.70
-2.9133
0.7867
one significant figure after decimal point
round off to 90.4
two significant figures after decimal point
round off to 0.79
43
Significant Figures
Multiplication or Division
The number of significant figures in the result is set by the original
number that has the smallest number of significant figures
4.51 x 3.6666 = 16.536366 = 16.5
3 sig figs
round to
3 sig figs
6.8 ÷ 112.04 = 0.0606926 = 0.061
2 sig figs
round to
2 sig figs
44
Significant Figures
Exact Numbers
Numbers from definitions or counted numbers of objects are
considered to have an infinite number of significant figures
The average of three measured lengths; 6.64, 6.68 and 6.70?
6.64 + 6.68 + 6.70
= 6.67333 = 6.67 = 7
3
Because 3 is an exact number
45
Carry out the following arithmetic operations to
the correct number of significant figures.
11,254.1 g + 0.1983 g
66.59 L – 3.113 L
8.16 m x 5.1355
0.0154 kg ÷ 88.3 mL
2.64x103 cm + 3.27x102 cm
46
Carry out the following arithmetic operations to
the correct number of significant figures.
26.5862 L+ 0.17 L
9.1 g – 4.682 g
7.1x104 dm x 2.2654x102 dm
6.54 g ÷ 86.5542 mL
7.55x104 m – 8.62x103 m
47
Problem 1.36
Carry out the following operations as if they were
calculations of experimental results, and express each
answer in the correct units with the correct number of
significant figures
a)
b)
c)
d)
7.310 km ÷ 5.70 km
(3.26 x 10-3 mg) – (7.88 x 10-5) mg
(4.02 x 106 dm) + (7.74 x 107 dm)
(7.8 m – 0.34 m)/(1.15 s + 0.82 s)
48
Accuracy – how close a measurement is to the true value
Precision – how close a set of measurements are to each other
accurate
&
precise
precise
but
not accurate
not accurate
&
not precise
49
Problem 1.38
Three apprentice tailors (X,Y, and Z) are
assigned to the task of measuring the seam of a
pair of trousers. The results in inches are:
X (31.5, 31.6, 31.4)
Y (32.8, 32.3, 32.7)
Z (31.9, 32.2, 32.1)
The true length is 32.0 in. Comment on the
precision and accuracy of each tailor’s
measurements.
50
Dimensional Analysis Method of Solving Problems
1. Determine which unit conversion factor(s) are needed
2. Carry units through calculation
3. If all units cancel except for the desired unit(s), then the
problem was solved correctly.
given quantity x conversion factor = desired quantity
given unit x
desired unit
given unit
= desired unit
51
Dimensional Analysis Method of Solving Problems
How many mL are in 1.63 L?
Conversion Unit 1 L = 1000 mL
1000 mL
1.63 L x
= 1630 mL
1L
2
1L
L
1.63 L x
= 0.001630
1000 mL
mL
52
The speed of sound in air is about 343 m/s. What is this
speed in miles per hour?
conversion units
meters to miles
seconds to hours
1 mi = 1609 m
1 min = 60 s
1 mi
60 s
m
x
x
343
s 1609 m
1 min
1 hour = 60 min
60 min
mi
x
= 767
hour
1 hour
53
Problem 1.46
The current speed limit in some states in
the US is 55 miles per hour. What is the
speed limit in km/hr? (1 mi = 1609 m)
54
Problem 1.66
Vanillin is the substance whose aroma the
human nose detects in the smallest
amount. The threshold limit is 2.0 x 10-11g
per liter of air. If the current price of 50 g
of vanillin is $112, determine the cost (in
cents) to supply enough vanillin so that
the aroma could be detected in a large
aircraft hanger with a volume of 5.0 x 107
ft3
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