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1.1. Chemistry is important for anyone studying the sciences
1.2. The scientific method helps us build models of nature
1.3 Matter is composed of elements, compounds, and mixtures
1.4. Properties of matter can be classified in different ways
1.5 Measurements are essential to describe properties
1.6. Measurements always contain some uncertainty
1.7. Units can be converted using the factor-label method
1.8. Density is a useful intensive property
1.1. Chemistry is important for anyone studying the sciences 3
Chemistry and the Sciences
• Chemistry- the study of the composition of matter and its transformations
• Matter- anything that takes up space and has mass• Chemical reaction- change that results from the
interaction of matter.
1.2. The scientific method helps us build models of nature 4
Scientific Method : Getting Started
Observe a Phenomenon-accurately describe something we see, taste, feel,
smell or hear
Pose A Question To Explain The Phenomenon
Form a Hypothesis-a tentative explanation of
the phenomenon
1.2. The scientific method helps us build models of nature 5
Scientific Method: Testing the Hypothesis
Experiment to Prove or Disprove Hypothesis
If experiment proves hypothesis,
form theory (theoretical model)
If experiment disproves hypothesis,
Pose new question or hypothesis
Continue experimentation. If results form pattern,
considered a law
1.2. The scientific method helps us build models of nature 6
Scientific Method Case Study: The Process of Growth
• A child sees that a seed, when planted in soil, watered, and exposed to sunlight, grows to form a flower. He concludes that all living things require sunlight, water, and burial in soil to grow.
• Build a case for rebuttal using the scientific method.
1.2. The scientific method helps us build models of nature 7
Your Turn!
Which of the following is not a hypothesis for the observed plant growth?A. soil is necessary to all growth
B. light is essential to growth of the seed
C. water is required to allow growth
D. plants grow to a greater height if they receive fertilizer
E. none of the above
1.2. The scientific method helps us build models of nature 8
Your Turn!
A chicken egg is buried, left in the sun, and watered. A second egg is left above the soil, watered and left in the sun. Would this prove that soil is necessary to growth?
A. Yes
B. No
1.2. The scientific method helps us build models of nature 9
The Scientific Method- Evaluating The Data
A theory is an explanation (based on well-tested, internally consistent experimental results) about why the phenomenon may occur it should explain currently available data It should be as simple as possible It should clearly show underlying connections It should accurately predict future behaviors
1.2. The scientific method helps us build models of nature 11
Atomic Theory Helps Us Visualize Matter
• Air inflates a balloon air must be composed of matter the matter is colliding with the walls
of the container.
• A leaf floats on water’s surface water is composed of particles that
occupy space
• A leaf falls through air, but rests on water’s surface particles are closer in liquid than in
gases
1.3. Matter is Composed of Elements, Compounds, and Mixtures 13
Changes in Matter
• Chemical change- a process that results in the formation of a new substance
• Evidence? Formation of a new solid, new liquid, new gas, temperature change, or an unexpected color change
• Physical change- a process that results in no new substance, but that may change the state of those present, or the proportions
1.3. Matter is Composed of Elements, Compounds, and Mixtures 14
Learning Check: Chemical Or Physical Change?
Chemical Physical
Magnesium burns when heated in a flame
Magnesium metal tarnishes in air
Magnesium metal melts at 922K
Grape Kool-aid lightens when water is added
1.3. Matter is Composed of Elements, Compounds, and Mixtures 15
Your Turn!
Which of the following is not a chemical change?A. a match burns in air
B. ice melts in air
C. an aluminum door whitens in air
D. all of these
E. none of these
1.3. Matter is Composed of Elements, Compounds, and Mixtures 16
• Matter is either a pure substance or a mixture• Mixtures may be separated using physical methods
such as chromatography, filtration, sieving
Matter Can Be Classified By Its Properties:
1.3. Matter is Composed of Elements, Compounds, and Mixtures 17
What Is An Element?
• Elements - substances that cannot be decomposed into simpler substances
• shown on the periodic table as symbols: “K” for potassium and “Na” for sodium
• made of identical atoms, either singly or in groups
1.3. Matter is Composed of Elements, Compounds, and Mixtures 18
Weird Science
• Eleven symbols bear no resemblance to their English names - their names are derived from other languages
• Some of these are used in naming, and these are highlighted
Sb antimony stibium K potassium kalium
Cu copper cuprum Sn tin stannum
Au Gold aurum Na sodium natrium
Ag silver argentum W tungsten wolfram
Fe iron ferrum Hg mercury hydragyrum
Pb lead plumbum
1.3. Matter is Composed of Elements, Compounds, and Mixtures 19
What Is A Compound?
• Compounds - formed from two or more atoms of different elements combined in a fixed proportion
• Have different characteristics than the elements that compose them
• Can be broken down into elements by some chemical changes
1.3. Matter is Composed of Elements, Compounds, and Mixtures 20
Mixtures
• mixtures consist of varying amounts of two or more elements or compounds
• Homogeneous mixtures or “solutions”- have the same properties throughout the sample Brass, tap water
• Heterogeneous mixtures- consist of two or more phases Salad dressing, Coca-Cola ™
1.3. Matter is Composed of Elements, Compounds, and Mixtures 21
Learning Check: Classification
Sand Ice
(H2O)
Flour Table Salt (NaCl)
Pure
Element
Compound
Molecule
Heterogeneous Mix
Homogeneous Mix
1.3. Matter is Composed of Elements, Compounds, and Mixtures 22
Your Turn!
• brass is pure
• natural peanut butter made only by crushing peanuts is pure
• because blood cells can be distinguished from plasma under a microscope, blood is a heterogeneous mixture:
• True• False
• True• False
• True• False
1.4. Properties of matter can be classified in different ways 23
Classification Of Matter By State
Classification by state is based on packing, motion, and shape Solids have fixed shape and volume Liquids have fixed volume, but take the container shape Gases have to expand to fill the shape and volume of
the container
1.4. Properties of matter can be classified in different ways 24
Properties Of Matter
• Chemical properties describe the behavior of the matter that leads to the formation of a new substance: the "reactivity" of the substance
• Physical properties can be observed about the matter alone, without changing the composition
1.4. Properties of matter can be classified in different ways 25
Learning Check: Chemical or Physical Property?
Chemical Physical
Magnesium metal is grey
Magnesium metal tarnishes in air
Magnesium metal melts at 922K
Magnesium reacts violently with hydrochloric acid
1.4. Properties of matter can be classified in different ways 26
Your Turn!
Which of the following is a chemical property?
A. water is colorless
B. water reacts violently with solid Na metal
C. water dissolves table salt
D. all of these
E. none of these
1.4. Properties of matter can be classified in different ways 27
Intensive And Extensive Properties
• Intensive properties are independent of sample size Examples: color, texture and temperature
• Extensive properties depend on sample size Examples: volume and mass
• Properties used to identify substances are always intensive Density, color, and texture are often helpful in
identification, but temperature is not
1.5 Measurements are essential to describe properties 28
Measurements are Observations
• Qualitative observations are non-numerical-- ask “what” or “how” or “why”
• Quantitative observations are numerical--ask “how much” and are also called measurements
• This course is general chemistry with quantitative analysis
1.5 Measurements are essential to describe properties 29
Your turn!
Which of the following is a quantitative observation?
A. the height of the plant
B. the mass of water added
C. the temperature of the day
D. all of the above
E. none of the above
1.5 Measurements are essential to describe properties 30
• Always involve a comparison
• Require units
• Involve numbers that are inexact (estimated). This uncertainty is due to the limitations of the observer and the instruments used
• In science, all digits in a measurement up to and including the first estimated digit are recorded
Measurements:
1.5 Measurements are essential to describe properties 31
Measurements and units
• In the U.S., we use the Imperial (USCS) System
• The scientific community (and most of the world) uses the metric system
• Variations in the metric system exist, thus a standard system is used: International System of Units (SI)
• SI units we will use now: Length (m) Mass (kg) Time (s) Temperature
(K)
1.5 Measurements are essential to describe properties 32
Measurement Formula SI UnitsArea length × width m2
Volume length × width × height m3 Velocity distance/time m/sAcceleration velocity/time m/s2 Density mass/volume kg/m3
Derived units
involve a combination of base units, including:
1.5 Measurements are essential to describe properties 33
Decimal multipliers
Prefix (Symbol) = Numerical Equivalent• Giga ( G ) = 109
• Mega- ( M ) = 106
• kilo- ( k ) = 103
• centi- ( c ) = 10-2
• milli- ( m ) = 10-3
• micro- ( μ) = 10-6
• nano- ( n ) = 10-9
• pico ( p ) = 10-12
1.5 Measurements are essential to describe properties 34
Learning Check: Complete The Missing Information
kg
10-12 g
nm
106 g
cL
109 Hz
10-9 m
10-2 L
pg
Mg
GHz
103 g
1.5 Measurements are essential to describe properties 35
Your Turn!
Identify the correct conversion:
A. Gm=109 m
B. 109 Gm = m
C. Gm = 10-9 m
D. none are correct
1.5 Measurements are essential to describe properties 36
You May Encounter Non-SI Metric Units:
measurement name symbol Value
length angstrom Å 10-10m
mass amu
metric ton
u
t
1.66054×10-27 kg
103 kg
time minute
hour
min
h
60 s
3600 s
volume liter L 1000 cm3
1.5 Measurements are essential to describe properties 37
Mass- Matter Content
USCS: oz (avdp.), lb, T
Metric: g
SI: kg
1.5 Measurements are essential to describe properties 38
Length
USCS: in, ft, yd, mi
Metric: L, cm3
SI: m
1.5 Measurements are essential to describe properties 39
Volume-bulk
• measured directly, using equipment for volumetric measure
• calculated using dimensional (length) information and appropriate formulas. 1 cm3= 1mL
• USCS: fl. oz., pt., qt., gal
• Metric: L, cm3
• SI: m3
1.5 Measurements are essential to describe properties 40
Your Turn!
Which of the following is not a USCS unit?
A. ft.
B. m
C. gal.
D. T.
1.5 Measurements are essential to describe properties 41
Your Turn!
Which of the following is not a volume unit?
A. mL
B. qt
C. in3
D. cm
1.5 Measurements are essential to describe properties 43
Temperature Conversions
C 1 K1
C15.273CK tT
F32C5F9
CF
tt
1.5 Measurements are essential to describe properties 44
Complete The Following:
• 13.5°C=? °F
• 27.50 °F =? °C
• -34.5 °F =?K
F
FCC
FF
t
3.56323.24
325.135
9
CC
tF
CF
Ct
F
CFFt
Ct
C
FFFt
FC
tC
FFt
50.29
5
1
3250.27
9
5
1
32
5
932
325
9
KC
tK
T
CC
tF
CF
Ct
F
CFFt
2.23615.273
449.369
5
1
325.34
9
5
1
32
1.5 Measurements are essential to describe properties 45
Your Turn!
Which of the following is the lowest temperature?
A. 300. K
B. 16 ºC
C. 55 ºF
D. they are the same
1.6. Measurements always contain some uncertainty 46
• Because each measurement involves an estimate, measurements always have error.
• Record all measured numbers, including the first estimated digit
• These digits are called significant digits or significant figures
• Exact numbers have infinite significant digits
Measurement Error
1.6. Measurements always contain some uncertainty 47
Significant Digits In A Measurement Are Limited By Instrument Precision
• Using the first thermometer, the temperature is 21.3 ºC (3 significant digits)
• Using the more precise (second) thermometer, the temperature is 21.32 ºC (4 significant digits)
1.6. Measurements always contain some uncertainty 48
• Errors-inherent error due to the equipment or procedure Changing volume due to thermal expansion or contraction
(temperature changes) Improperly calibrated equipment procedural design allows variable measurements
• Mistakes-blunders that you know that you have made. Do not use these data Spillage Incomplete procedures Reading scales incorrectly Using the measuring device incorrectly
Errors Arise From A Number Of Sources Including:
1.6. Measurements always contain some uncertainty 49
Reducing Error:
• Errors can often be detected by making repeated measurements
• Error can be reduced by calibrating equipment
• The average or mean reduces data variations: it helps find a central value
1.6. Measurements always contain some uncertainty 50
• An accurate measurement is close to the true or correct value, a “hole-in-one”
• A precise measurement is close to the average of a series of repeated measurements
• When calibrated instruments are used properly, the greater the number of significant figures, the greater is the degree of precision for a given measurement
Accuracy vs. Precision
1.6. Measurements always contain some uncertainty 51
• Non-zero digits are significant
• Zeros between significant digits are significant
• Zeros to the right of non-zero digits in a number that contains a decimal point are significant (Trailing with a decimal point)
• Zeros to the left of the first nonzero digit are never counted as significant (Leading)
• Zeros at the end of a number without a decimal point are assumed not to be significant (Trailing without a decimal place)
Rules For Significant Figures (Sig Figs)
1.6. Measurements always contain some uncertainty 52
Learning Check: How Many Significant Figures Are There In The Following?
2.33 3
500.0 4
1000 1
.0500 3
1.6. Measurements always contain some uncertainty 53
Your Turn!
How many sig. figs. are there in the number 010.010?
A. 2
B. 3
C. 4
D. 5
E. none of these
1.6. Measurements always contain some uncertainty 54
Rules for combining measurements depend on the type of operation performed:
• Multiplication and division The number of sig. figs in the answer should not be
greater than the number of sig. figs in the factor with the fewest sig. figs
figs.) sig. (2
13
figs.) sig. (2figs.) sig. (4 figs.) sig. (3
0.642.751 3.14
Measurements Limit The Precision Of Calculated Results
1.6. Measurements always contain some uncertainty 55
Your Turn!
How many sig. figs. result from the following:
12.33 x 0.00002?
A. 2
B. 3
C. 4
D. 5
E. none of these
Only 1!
1.6. Measurements always contain some uncertainty 56
The answer should have the same number of decimal places as the quantity with the fewest number of decimal places (least precise)
3.247 ← 3 decimal places 41.36 ← 2 decimal places +125.2 ← 1 decimal place 169.8 ← answer rounded to 1 decimal place
Addition and Subtraction
1.6. Measurements always contain some uncertainty 57
Your Turn!
How many sig. figs. result from the following:
10.33-0.0344?
A. 2
B. 3
C. 4
D. 5
E. none of these
1.6. Measurements always contain some uncertainty 58
Exact Numbers
• Numbers that come from definitions are exact and have no uncertainty
• They can be assumed to contain an infinite number of significant figures
1.6. Measurements always contain some uncertainty 59
Your Turn!
How many sig. figs. result from the following?
A. 2
B. 3
C. 4
D. 5
E. none of these
2.2
12.2-10.88) x (10.0
1.7 Units can be converted using the factor-label method 60
Unit Conversions
• Suppose we wish to convert 25 miles to km. Further, we know that there are .6215 miles in a km.
• We can assemble a ratio and solve this problem.
easy enough because we have a direct conversion between the units
Often, we must piece together multiple steps and this approach is impractical
1km
miles 0.6215
km ?
miles 25
1.7 Units can be converted using the factor-label method 61
Definitions of One
• Remember that 3 teaspoons (tsp) = 1 tablespoon (Tbsp)
• Using the logic that a number divided by its equivalent = 1, then it follows that:
• Clearly 3/1 is not 1, but the units make the statement true.
• Thus we could multiply any number by either of these fractions (1) and the number has the same value.
13tsp
1Tbsp and 1
1Tbsp
3tsp
1.7 Units can be converted using the factor-label method 62
Learning CheckWrite two fractions from the following conversion factors
• 4 qt = 1 gal
• 8 fl oz=1 c
• 16 oz. = 1 lb
4 qt/ 1gal 1 gal/4 qt
8 fl oz / 1c and 1c/ 8 fl oz
16 oz./1 lb and 1 lb/16 oz.
1.7 Units can be converted using the factor-label method 63
Using Conversion Fractions
• Since we can multiply by “1” and the value remains unchanged, we can multiply by these conversion fractions to change the units of a measurement.
• For example, 12 in = 1 ft so the conversion of 3.5 ft to in. can be done using one of these two conversion fractions
1
5.3 ft
112in
1ft and 1
1ft
12in
inft
in42
1
12
1.7 Units can be converted using the factor-label method 64
Your Turn!
Given that 2.205 lb=1 kg, which of the following is an appropriate conversion factor?
kg 1
lb 1
kg 2.205
lb 2.205kg 1
lb 2.205
kg 2.205
lb 1 None of these
E.D.C.B.A.
1.7 Units can be converted using the factor-label method 65
USCS Unit Conversions
Mass Volume Distance16 oz. (avdp.) = 1 lb.2000 lb. = 1 T.
3 tsp. = 1 Tbsp.16 Tbsp. = 1 c.2 c. = 1 pt.2 pt. = 1 qt.4 qt. = 1 gal.8 fl. oz. = 1 c.
12 in. = 1 ft.3 ft. = 1 yd.1760 yd. = 1 mi.
1.7 Units can be converted using the factor-label method 66
USCS to Metric Metric to USCS Length 1 in. = 2.54 cm 1 m = 39.37 in
1 yd = 0.9144 m 1 km = 0.6215 mi1 mi = 1.609 km
Mass 1 lb = 453.6 g 1 kg = 2.205 lb1 oz = 28.35 g
Volume 1 gal = 3.785 L 1 L = 1.0567 qt1 qt = 946.4 mL1 oz (fluid) = 29.6 mL
It is also useful to know that 1 mL = 1 cm3=1 cc
USCS And Metric Units Are Related Using “Critical Links”
1.7 Units can be converted using the factor-label method 67
Building Conversion Factors in Unit Conversions
1. Write the number to be converted as a fraction (with units)
2. Identify the target units3. Are the starting units in the same system as the
target? If not, you will need a critical link. USCS→USCS Conversions: Write down the
conversion factors from smallest to largest . metric →metric conversions: Write down the
definitions of all prefixed units.
1.7 Units can be converted using the factor-label method 68
Learning Check:
Write all conversion factors needed to convert the following:
• 33 in to yd
• 450 c to gal
• 56 y to s
• 25 mph to ft/s
• 12 in.=1 ft• 3 ft =1 yd• 2 c.=1 pt.• 2 pt.=1 qt.• 4 qt.=1 gal.• 60 s=1 min• 60 min=1 h• 24 h=1 da• 365.25 da=1 y• Distance: 3 ft=1 yd; 1760 yd=1 mi• Time: 60 s=1 min; 60 min=1 h
1.7 Units can be converted using the factor-label method 69
Learning Check:
Write all conversion factors needed to convert the following:
• 33 mm to km
• 450 cg to ng
• 56 µs to Ms
• 25 mL to nL
• mm=10-3 m• km=103 m• cg=10-2 g• ng =10-9 g• μs=10-6 s• Ms=109 s• mL=10-3 m • nL=10-9 L
1.7 Units can be converted using the factor-label method 70
Learning Check:Write Down All Conversion Factors Needed To Convert
The Following:
• 3.03 g to T
• 0.545 ft to km
• 25 mph to km/s
•Crit. Link: 453.6 g=1 lb
•US→US: 2000 lb = 1 T
•CL: 2.54 cm=1 in
•US→US: 12 in=1 ft
•m→m: cm=10-2 m; km=103 m
•Distance: CL: 2.54 cm =1 in
•US→US 12 in = 1 ft; 3 ft= 1 yd; 1760 yd = 1 mi;
•m →m: cm = 10-2 m; km= 103 m
Time:
60 s=1 min
60 min= 1 h
1.7 Units can be converted using the factor-label method 71
Building Conversion factors (cont).
4. Use the form of the conversion factor that allows the units to cancel--they must be on opposite levels of the fraction to cancel.
5. Continue adding conversion factors until the units match the target units.
2nd Check- are all units written on the page two times? If so, you have enough info to start the problem.
1.7 Units can be converted using the factor-label method 72
Learning Check:
Convert the following:
• 3.03 g to tons
• 0.545 ft. to km
• 5.22 y to s
• 25 mph to km/s
•3.34(10-6) T
•1.66(10-4) km
•1.65(108) s
•1.1(10-2) km/s
1.7 Units can be converted using the factor-label method 73
Your Turn!
Given that 2.205 lb = 1 kg, what is the mass of 23.3 lb expressed in kg?
A. 51.4 kg
B. 0.0946 kg
C. 10.6 kg
D. none of these
1.7 Units can be converted using the factor-label method 74
Your Turn!
Given that 2.54 cm = 1 in, how many km are there in 25 ft?
A. 7.6 km
B. 0.10 km
C. 762 km
D. none of these 7.6(10-3) km!
1.8. Density is a useful intensive property 75
Density (d)
• intensive property defined as the ratio of an object’s mass (m) to volume (v), d = m/v
• characteristic of pure substances at a specified temperature
• Since most substances expand when heated, densities decrease when heated.
• units : g/L for gases and g/mL for solids and liquids.
1.8. Density is a useful intensive property 76
Density relates a sample mass and volume
• Blood has a density of 1.05 g/cm3
• We can say that 1.05 g of blood is equivalent to 1.00cm3
• Conversion factors can be constructed from this equivalence, which could be used in the factor-label method
blood g 1.05
bloodcm 1.00or
bloodcm 1.00
blood g 1.05 3
3
1.8. Density is a useful intensive property 77
Learning Check:
A crash sounds from the lab- a large vial of mercury has fallen from a broken shelf. We call the hazardous materials team to report the spill, about 2.0 quarts of mercury. They ask for the mass- what is it? (hint: d=13.69g/mL)
gmL
g
L
mL
qt
Lqt)10(6.2
69.13
100567.1
1
1
0.2 43