chem 121 - general chemistry chapter 1

7/29/2019 CHEM 121 - General Chemistry Chapter 1

1/14

CHEMISTRY 121General Chemistry I

Instructor: Prof. D. B. Jacobson

Textbook: Chemistry 11th Ed.

byChang, Goldsby

Student Assistance:

Office Hours: 10:00-10:50 AM MWFOffice: Ladd [email protected]

Dr. Mel Morris (Professor Emeritus)Tutors students in Ladd 104D1:00-3:30 PM M-F and byappointment (231-7011)

Course Policies: See syllabus for details (read).

Grading:Four 100 point examsFifth (final) exam (100 points)online homework (40 points)

Grading scale is under course policies.

The best three of the first four examsare counted toward your score (the lowestexam score is dropped). The fifth (final)exam can not be dropped.

On-line homework (Connect)

The Connect on-line homework is included with thetextbook in the bookstore (ca. $195). You can buy theConnect card separately from McGraw-Hill.

Registration information is on Blackboard(Announcements). Just follow the instructions. The codeyou enter for registration is on the Connect card in yourex oo .

There will be 10 on-line homework assignments (eachabout 15 questions). The lowest two scores will bedropped (only the highest eight count in your grade).The on-line homework will be worth a total of 40 points.Make sure you know the due date for the assignmentand do not forget to submit your homework. You willhave 3 attempts to get a question right.

THERE ARE NO MAKEUP EXAMS IN THISCLASS

A missed exam, for any reason, is scored as azero and is the one that will be dropped. Ifyou miss an exam for a legitimate reason, youshould let me know o the circumstances assoon as possible. If you have a conflict andare unable to take an exam, you can takeexams early in Ladd 104. To take an examearly you need to schedule a time with thesecretary (Wendy Leach, phone 1-8751) in

Ladd 104.

CHAPTER 1Chemistry: The Study of

Chemical Change

Chemistry: The study of matter and how the

properties of matter are related tocomposition.

Matter: Anything that has mass andoccupies space.

Mass: A measure of the amount of matter-isindependent of gravitational force.


2/14

CONTRAST MASS WITH WEIGHT

Weight: Depends on gravitational

force.

Wei ht is defined as mass m Xacceleration (a) due to gravity (g):

The force of attraction by theearth:

F = (m)(a) or W(weight) = (m)(g)

On Earth, g = 9.8 m/s2 at sea level

On the Moon, g = 1.7 m/s2 (1/6)

Weight varies depending on the force ofgravity (g).

A 200 pound person on Earth weighs only 34pounds on the Moon.

An object has a different weight on the Moonthan it does on Earth (gravity) but its mass is

the same (constant).

In outer space, an object can be weightless,yet it has the same mass as on earth. We candetermine mass in outer space by simplymeasuring the acceleration due to an appliedforce:

a

FmmaF ;

There are only four fundamental forces innature:

Gravitational - mysteriousElectromagnetic (Chemistry)StrongWeak

nucleus

Chemistry is critical to modern society; How?

Technologies

Electronics (microprocessors, transistors)

Materials (polymers, ceramics, coatings)

Medical (medicines, diagnostics)

Personal and Home care products

Energy (Batteries, photovoltaic cells, fuel cells)

Many other modern products

CHEMISTRY HAS CONSEQUENCES

POLLUTION

GLOBAL WARMING

WARFARE

ACCIDENTS (ammonia spill in Minot)

BALANCE THE BENEFITS WITH RISKS

The earth's temperature has risenby about 1.5 oF the past century!!!

WHY ?

Global Warming ???(Green House Effect)

Probably because of increases inconcentration of greenhouse gases(mainly CO2 ).

CO2 produced from combustion offossil fuels.


3/14

Avg.temp.57 F

No greenhouse gasses average earth temp. = 0 F

Absorption of Infrared (heat) Radiation

CO2 concentration in the atmosphere


4/14

Earth:

CO2 absorbs infrared radiation (heat).

Concentration of CO2 in the atmosphere hasincreased by 25 % in the past 100 years.

Earths temperature has risen by about 1.5 oF(1 oC) in that time (predict 4-9 oF increase by2100).

The difference in global temperatures betweentoday and the last ice age is only 5 7 oF.

OZONE DEPLETION !!

What Is Ozone ?????

Form of Elemental Oxygen with three Oatoms bonded together (O3).

Shields earth from harmful ultravioletradiation from sun (ca. 15 miles up).

O3 O2 + O

UV

Light

Chlorofluorocarbons (CFCs): Have beenimplicated in ozone depletion.

Reactions in the upper atmosphere

CF2Cl2 CF2Cl + ClLight

Cl + O3 ClO + O2

ClO + O Cl + O2

2 ClO 2 Cl + O2

Hence, one CFC molecule can destroythousands of ozone molecules.

Observation in 1985

Crutzen, Molina, Rowland: Nobel prize(1995) in chemistry for their discoveryof ozone depletion by CFCs in 1974.

CONSEQUENCES of ozone depletion?

Increased skin cancers, crop damage,eye cataracts, etc.

Both global warming and ozone depletionare complex and not completelyunderstood.


5/14

Chemistry Science

Experiments Explanationstest(measurements, why ?

observations)

Do further experiments to test theinitial explanation of results.

WHAT TYPES OFEXPERIMENTS?

Two approaches

1) support the ideas

2 dis rove the ideas or ex lanations

(natural or

scientific)

Observations Facts Law

LAW: A verbal statement or mathematicalequation that summarizes observations andexperiments.

Example:Law of gravity: Two objects areattracted to each other.

Force of gravity = 9.8 m/s2 on earth

Law: Not an explanation of nature, simplyshows a physical relationship.

Newtons Universal Law of Gravity:

221ForcenalGravitatio

r

mGmF

G: universal gravitational force constant -11 2 2.

r: distance between object centers

m1 and m2: masses of the two objects

Calculate the mass of the earth

Force due to an apple falling from tree:

mgFappleofweight

Use Newtons Universal Law of gravity:

2AppleonForcenalGravitatio

r

GmMF

m is apple mass and M is the earths mass, r isthe distance between object centers (earthsradius)

For both equations, the force, F, is thesame. Hence, we can set the two equationsequal to each other and solve for the earthsmass:

mgr

GmMF

2

Note: The mass, m, of the apple cancelsout of the equation.Rearrange the equation in terms of M:

kg10X6

/kgmN10X6.67

m10X6.4m/s9.8

24

2211

2622

G

grM


6/14

Explanations: Why nature behaves the wayit does (hypothesis).

Hypothesis: A tentative (initial)explanation of the observations.

Law of gravity: Objects attract eachother... Why?? gravityWe use a Hypothesis to try to explainhow and why this occurs!!!!

HYPOTHESIS

Test the hypothesis; modify it to fit newexperimental results/observations/facts.

After a hypothesis has undergone extensivetesting and modification, it can evolve into a

.

Theory: A hypothesis that repeatedly withstandsthe test of experiments and has overwhelmingsupportive evidence.

Theories Must be tested, generally havepredictive power.

THEORIES

Can never be proven, but can bedisproven or found to be in error.

Some examples include:

Theor of Evolution

Theory of Relativity

Atomic Theory

Quantum Mechanics Theory

SCIENTIFIC METHOD

PROPERTIES OF MATTER

Every substance (matter that has a definiteor constant composition and distinctproperties) has a unique set of properties(physical and chemical).

ys ca proper es: an e measure anobserved without changing theidentity/composition of the substance.

Examples:melting & boiling points, density, mass,

volume, color, shape


7/14

Chemical properties: Describe the way asubstance reacts to form other substances(reactivity). The identity/composition ischanged.

Combustion reaction (reaction with O2):

Decomposition reaction:

C12H22O11 12 C + 11 H2Oheat

Table SugarElementalCarbon Water

Combination reaction:

2 Na + Cl2 2 NaCl

elemental elemental tablesodium chlorine salt

Violent reaction!!!

Both elemental sodium and chlorine are verydeadly (Cl2 was the first poison gas used inWWI).

NaCl (table salt) is an essential nutrient.

2 Na + Cl2 2 NaCl

Properties can be either extensive or intensive.

Extensive properties: Value depends on thequantity of matter.

Examples: Mass, Volume (solid orliquid), Heat, etc.

Intensive properties: Value does not depend onthe quantity of matter. They can be used toidentify a substance.

Examples: Melting and Boiling points,Density, Temperature, etc.

Measurements Quantitative

What kind of measurements?

length

mass

time

temperature

length = 3.61 (magnitude)

without units, this number ismeaningless

Attach units to give meaning, e.g., 3.61 feet

(units)

UNITS ARE VERY IMPORTANTNEED A CONSISTENT SET OF UNITS

International System Of Units (SI)Based on the metric system

SI Base Units (Table 1.2) KNOW THIS TABLE!!!!!

Quantity Unit Symbol

Length meter m

Mass kilogram kg

Time second s (not sec)

Temperature kelvin K

Amount of

Substance

mole mol


8/14

Metric system: Initiated by the FrenchAcademy of Sciences in 1790s.

Metric system decimal system, based onmultiples of ten

: = =.millimeters

English: 1.00 yard = 3.00 feet = 36.0 inches

Prefix Abb. (symbol) Multiple

giga-

mega-

G

M

109 (1,000,000,000)

106 (1,000,000)

kilo- k 103 (1,000)

Decimal multipliers SI prefixesTable 1.3 KNOW THIS!!!!

ec - - .

centi- c 10-2 (0.01)

milli- m 10-3 (0.001)

micro- 10-6 (0.000001)nano- n 10-9 (0.000000001)

pico- p 10-12 (0.000000000001)

femto- f 10-15 (0.000000000000001)

Selected SI Prefixes for length

Greek prefixes for values larger than the basevalue (kilo, mega, giga).

Latin prefixes for values smaller than the basevalue (centi, milli, micro)

Multiplier relationshipsfor length

1 Gm = 1 X 109 m1 Mm = 1 X 106 m1 km = 1 X 103 m

1 dm = 1 X 10-1 m1 cm = 1 X 10-2 m1 mm = 1 X 10-3 m1 m = 1 X 10-6 m1 nm = 1 X 10-9 m1 pm = 1 X 10-12 m1 fm = 1 X 10-15 m


9/14

Scientific notation: A more convenient way ofexpressing very large or very smallnumbers.

1,000,000,000 1 X 109 (a billion)

0.00000136 1.36 X 10-6 (a millionth)Move the decimal for very large or verysmall numbers to the left and right.

KNOW HOW TO USE IT!!!!!!!!

DERIVED UNITSVolume (length)3, m3, cm3

Density (d) mass per unit volumed= mass/volume (Units g/cm3, kg/m3)

Density is a characteristic physical property of asubstance.

OTHER DERIVED UNITS:

area (length)2, speed (distance/time),

acceleration (distance/time2), energy, force, etc.

VOLUME - DIFFERENT UNITS

1 m3 = 1 X 106 cm3

1 m3 = 1 X 103 dm3

1 dm3 = 1 liter (L)

1 L = 1000 mL = 1000 cm3

1 mL = 1 cm3

Liter (L), milliliter (mL), and cm3 Commonunits of volume

Volume relationships

Figure 1.10

Glasswareformeasuringvolume

Figure 1.8


10/14

CALCULATIONSCalculations typically involve convertingbetween units!!!!

Every numerical value should have units!!!

?????Given Units Desired Units

Use DIMENSIONAL ANALYSIS(conversion factors) in calculations (factorlabel method).

Carry units along in all calculations!!!

unitsDesiredunitsGiven

unitsDesiredunitsGiven

ConversionFactor

Given units X (Conversion Factor) = Desired units

Need to identify conversion factors (ratio ofunits) and use them appropriately.

Example:

How many cm3 are in 0.543 L (volume) ?

First, identify what is given (volume in L)an w at s es re vo ume n cm .

Second, use appropriate conversion factorsfor unit conversions.

1 L = 1000 cm3 (exactly)

Divide both sides of the equation by 1000 cm3 :

Conversion factor:

Based on this relationship:

L1

cm1000or

cm1000

L1 3

3

1cm1000

cm1000

cm1000

L133

Why not use 1L/1000 cm3 as the conversionfactor ??

(given units)(conversion factor) = desired units

33

cm543L1

cm1000L0.543

2L1

Because the correct units are not obtained(we have the incorrect units)!!!!

Choose the form of the conversion factorto give the correct units.

33 cm0.000543

cm1000

L0.543

Example:

How many mm are in 1.05 X 10-3 km?

Requires two sets of conversions:

km m mm

mm

km10X051 3-

.

km1

m10X1 3

m10X1

mm13-

310X1.05


11/14

Example:How many cm3 are in 1.00 m3 ?

Conversion factor: 1 cm = 1 X 10-2 m

363

2-

3cm10X1.00

m10X1

cm1m1.00

SECTION 1.8 Handling Numbers (learnon your own)

Precision and Accuracy; SignificantFigures

Note the use of cubic terms !

Temperature: A measure of hotness orcoldness of an object. Determines thedirection of heat flow.

Temperature is different from Heat.

Fahrenheit (F)Celsius (C)kelvin (K)

Fahrenheit Scale: Gabriel Fahrenheit(1686-1736), German physicist, defined 0 Fas the freezing point of water saturated withsalt (NaCl) and 100 F as normal bodytemperature (actually 98.6 F).

He used this salt solution because it wasthe lowest temperature that could bereproduced reliably.

Later, based on pure water:Water boils at 212 F and freezes at

32 F, a 180 F range.

Celsius Scale: Anders Celsius (1701-1744),Swedish astronomer.

Also based on pure water:Water boils at 100 C and freezes at 0 C,a 100 C range.

Sometimes, this scale is referred to as theCentigrade scale or degrees Centigrade. This isan inappropriate term for this temperature scale.

Relate F to C, need to use a conversion factor.

Range: 180 F = 100 C

1C100

C100

C100

F180

C5

F9

C10

F18

C100

F180

conversionfactor

conversion factor

reduced to smallestwhole numbers

One more complication to consider beforeconverting from F to C:

0 C = 32 F

0 F = -17.8 C

Different zeropoints!!!

To convert C to F, we need toconsider these different zero points:

F32C5

F9

CF tt


12/14

Convert F to C; rearrange the precedingequation:

F9

C5F32-C

Ftt

The value 32 is used to compensate forthe difference in zero points between thetwo scales.

Kelvin Scale

This is the SI temperature scale, SI unit oftemperature is the kelvin (K).

Kelvin and Celsius scales have the same stepsize (i.e., a change of 1 C is equal to a changeof 1 K .

Differ in zero points: (0 K = -273.15 oC)Hence, to convert between Celsius and kelvinscales, simply add or subtract 273.15:

TK = tC+ 273.15 or

tC= TK - 273.15

Figure 1.11

Heat and Temperature

Heat is an extensive property. Heat is themeasure of the total kinetic energy in an object.

Temperature is an intensive property.Temperature is a measure of the average kineticenergy in an object.

Consider two containers of water:

One has a volume of 1.00 L; the other has avolume of 0.10 L

Both at the same temperature (say 45 C); thecontainer with more water has more heat.

Classify matter based on composition andproperties.

Substance (pure): Matter that has adefinite or constant composition and

Classification of Matter

o e e .

CH4 -------- methane (natural gas)

O2 --------- diatomic oxygen

CH3CH2OH --- alcohol

Na --------- sodium metal

A substance has definite physical and chemicalproperties.

A substance can be either an element or acompound.

Element: A substance that cannot be decomposed

chemical means.

Elements are the building blocks of chemistry.

115? elements known; 82 naturally occurring


13/14

Elements: Names and Symbols

Name Symbol Latin Names

Hydrogen H

Carbon C

Calcium Ca

Oxygen O

o um a a r um

Potassium K Kalium

Iron Fe Ferrum

Tin Sn Stannum

Lead Pb Plumbum

Silver Ag Argentum

Copper Cu Cuprum

Table 1.1Page 12

Most elements are found in naturechemically combined with other elements.

Compounds: Substances composed of 2 ormore elements combined in fixed proportions(i.e., have a definite composition).

CH4 ------------ compound

CH3CH2OH ------- compound

O2 ------------- element

Na ------------- element

substances

For example, Ammonia (compound)

NH3 1.0000 g

0.1776 g H definite proportions

.

1.00 g H to 4.63 g N

Mixtures of Substances

Mixture: A combination of 2 or more

substances in which the substances retaintheir distinct identities.

xtures have var a e ar traryelemental composition.

A pure substance has a definitecomposition.

Two Types of Mixtures

Homogeneous: Mixtures that are uniformthroughout at the molecular level calledsolutions.

Exam les: Beer; Air; Salt dissolved in Water

Heterogeneous: Mixtures that are not uniformthroughout; do not have the same composition,properties, and appearance throughout.

Examples: Sugar & Salt; Sugar & Sand,Sand & Water

Mixtures can be separated into puresubstances by physical means.

Separation is based on different physicalproperties of substances in the mixture.

s a on, ra on, c roma ograp y

Local example: American Crystal Sugar

Oil Refineries


14/14

SIMPLE FILTRATION SETUP

Glass Funnel

lined withfilter paper

Glass Beaker

Simple Distillation Apparatus

Figure 1.5

Matter: Three states (physical forms) ofmatter.

(gas, liquid, solid)

Gas (vapor) No fixed volume or shape;expands to fill its container; fluid (flows).

Liquid Has a distinct volume but nospecific shape; fluid.

Solid Has a specific shape and volume;rigid.

chem 121 - general chemistry chapter 1

Documents