Transcript Chemistry 140

Welcome to CHEMISTRY !!!
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An Observational Science
An Experimental Science
A Laboratory Science
An Interesting Science
An Important Science
A “Hard” Science
What Happened To The Balloon?
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It was Whimpy and Broke!
It was fearful of all of the people!
Zoller scared it!
It got zapped by Klingons!
Hydrogen burns!
2H2 (g) + O2 (g) = 2 H2O (g) +
Energy
• Hydrogen and oxygen
are diatomic gases!
• Water can be a gas!
• ENERGY was given
off!-- This is
characteristic of an
Exothermic Reaction!
• This is a balanced
chemical reaction!
CHEMISTRY
The Study of
Matter and its Properties,
the Changes that
Matter Undergoes,
and the Energy
Associated with
those Changes
Chemistry as the Central Science
Oceanography
Atmospheric
Sciences
Physics
Economics
Medicine
Governments
Chemistry
People
Geology
Biology
Anthropology
Politics
Astronomy
Chemistry Homework !!!
“ Chemistry is not a spectator sport,
you must become involved, and that
means that you must do homework!”
Linus Pauling - 1967
Final Grade of Students Who Took Online Quizzes
3.4
3.23
3.2
3
3.03
2.98
2.9
2.87
Grade
3.1
3.04
2.8
2.64
2.6
2.49
2.4
2.38
2.2
2
0
1
2
3
4
5
Number of Quizzes Taken
6
7
8
9
Student versus Class Computer Notes
Student notes will have answers missing, and you will have to fill
Them in during or before class!
Class notes will have the answers in them, so you can copy them
down and have the answers. This requires you, the student to do
some writing during class in addition to the materials that I write
on the overheads. The reason for this is that you will remember
better by using more of your senses during class time.
Calculate the volume of a cube with sides of 2.0 inches?
Student:
Class notes:
2.0 in x 2.0 in x 2.0 in =
2.0 in x 2.0 in x 2.0 in = 8.0 in3
Suggestion : You do the work before class, and in that way learn
what is going to be done in class, then check in class!
Chemistry 142
Text: Chemical Principles
Fifth Edition - By Steven S. Zumdahl
Chapter #1 : Chemists and Chemistry
Chapter #2 : Atoms, Molecules, and Ions
Chapter #3 : Stoichiometry: Mole - Mass Relationships in
Chemical Systems
Chapter #21: The Nucleus: A Chemist’s View
Chapter #4 : Types of Chemical Reactions and
Solution Stoichiometry
Chapter #5 : Gases
Chapter #6 : Chemical Equilibrium
Chapter #7 : Acids and Bases
Chapter #8 : Applications of Aqueous Eqilibria
Chapter# 1 : Chemists and Chemistry
1.1 Thinking Like a Chemist
1.2 A Real-World Chemistry Problem
Stephanie Burns: Chemist, Executive
1.3 The Scientific Model
Critical Units!
1.4 Industrial Chemistry
1.5 Polyvinyl Chloride (PVC):
Real-World Chemistry
Chemical technicians check
water quality.
Figure 1.1: Chemists interact
Chemists at work
Source: Photo Researchers
Aciddamaged
paper
Source: Fundamental Photos
Figure 1.2
Paper: A Polymer called Cellulose
The Polymer cellulose, which consists of B-D-glucose monomers
Figure 1.3:
Schematic
diagram of the
strategy for
solving the
problem of the
acid
decomposition
of paper.
Artist's conception of the lost Mars
Climate Orbiter.
Source: NASA
Figure 1.4:
The various
parts of the
scientific
method
Industrial
processes
require
large
plants for
production
of
chemicals.
Source: Photo Researchers
Poly(Vinyl Chloride) (PVC) and Teflon
H
C
H
H
C
Cl
H
H
H
H
H
H
H
C
C
C
C
C
C
C
C
H
Cl
H
Cl
H
Cl
H
Cl
Vinyl chloride
F
F
C
n
PVC
F
C
H
F
F
F
F
F
F
F
F
C
C
C
C
C
C
C
C
F
F
F
F
F
F
F
F
F
Tetrafluoroethylene
Teflon
n
Scientist inspecting
Source: Corbis
Table 1.1 (P 12)
Type of Additive
Types of Additives Commonly Used in the
Production of PVC
Effect
Plasticizer
Softens the Material
Heat stabilizer
Increases resistance to thermal
decomposition
Ultraviolet absorber
Prevents damage by sunlight
Flame retardant
Lowers flammability
Biocide
Prevents bacterial or fungal attack
Definitions-I
Matter - The “stuff” of the universe: books, planets,
trees, professors - anything that has mass
and volume.
Composition - The types and amounts of simpler
substances that make up a sample of matter.
Properties - The characteristics that give each
substance a unique identity.
Physical Properties - are those the substance shows by
itself, without interacting with another substance
( color, melting point, boiling point,density, etc.)
Chemical Properties - are those that the substance shows
as it interacts with, or transforms into, other
substances (flammability, corrosiveness, etc.)
STATES OF MATTER and The World around US
• SOLID - The Earth
• LIQUID - Water
• GAS - The Atmosphere
Energy Involved in Phase Changes
Liberates
Energy
Gas
Boiling
Condensation
Liquid
Melting
Requires
Energy
Freezing
Solid
Definitions - II
Energy - The capacity to do work!
Potential Energy - The energy due to the position
of the object.Or Energy from a
chemical reaction.
Kinetic Energy - The energy due to the motion of
the object.
Units Used in Calculations
Length : A car is 12 feet long, not “12” !
A person is 6 feet tall, not “6” !
Area : A carpet measuring 3 feet(ft) by 4 ft has an area of:
( 3 x 4 )( ft x ft ) = _________ ft2
Speed and Distance : A car traveling 350 miles(mi) in
7 hours(hr) has a speed of:
350 mi / 7 hr = 50 mi / hr
In 3 hours the car travels:
3 hr x 50 mi / hr = ___________ mi
Derived SI Units
Quantity
Definition of Quantity
SI unit
Area
Length squared
m2
Volume
Length cubed
m3
Density
Mass per unit volume
kg/m3
Speed
Distance traveled per unit time
m/s
Acceleration
Speed changed per unit time
m/s2
Force
Mass times acceleration of object
Pressure
Force per unit area
Energy
Force times distance traveled
kg * m/s2
( =newton, N)
kg/(m2)
( = pascal, Pa)
kg * m2/s2
( = joule, J)
How to Solve Chemistry Problems
1) Problem: States all of the information needed to solve
the Problem.
2) Plan: Clarify the known and unknown.
Suggest the steps needed to find the solution.
Develop a “roadmap” solution.
3)Solution: Calculations appear in the same order as outlined.
4) Check: Is the result what you expect or at least in the same
order of magnitude!
5) Comment:Additional information as needed.
Conversion Factors : Unity Factors - I
Equivalent factors can be turned into conversion factors by
dividing one side into the other!
1 mile = 5280 ft
1 in = 2.54 cm
or 1 = 1 mile / 5280 ft = 5280 ft / 1 mi
or
1 = 1 in / 2.54 cm = 2.54 cm / 1 in
In converting one set of units for another, the one desired
is on top in the conversion factor, and the “old” one is
canceled out!
convert 29,141 ft into miles!
29,141 ft x 1 mi / 5280 ft = ______________ mi
Conversion Factors - II
1.61 km = 1 mi or
1 = 1.61 km / 1 mi
Convert 5.519 miles in to kilometers
5.519 mi x 1.61 km / mi = 8.89 km
conversions in the metric system are easy, as 1 km = 1000 m
and 1 meter (m) = 100 centimeters(cm)
and 1 cm = 10 millimeters(mm)
Therefore: into cm and mm!
8.89 km x 1000m / 1 km = 8,890 m
8,890 m x 100 cm / m = 889,000 cm
Conversion Factors - III
• Multiple conversion factors!
• Convert 3.56 lbs/hr into units of
milligrams/sec.
3.56 lbs x 1 kg x 1000g x 1000mg x 1 hr x 1 min =
hr
2.205 lbs 1 kg
1g
60 min 60 sec
= ____ mg/ sec
Conversion Factors - IV
metric volume to metric volume
• 1.35 x 109 km3 = volume of world’s oceans
• 1.35 x 109 km3 x (103 m/1 km )3 x ( 103 l/m3)
= 1.35 x 1021 liters
• conversion factors:
1000m = 1km
1000 l = 1m3
Conversion Factors - V
Calculate the mass of 1.00 ft3 of Lead
(density=11.4g/ml)?
• 1.00 ft3 x (12 in/ft)3 x (2.54 cm/in)3 =
28,316.84659 cm3
• 2.83 x 104 cm3 x 11.4 g/cm3 = 322,620.0000 g
• Ans. = 3.23 x 105 g = ________________ kg
An Example Problem!
The Volume of an irregularly shaped solid can be determined
from the volume of water it displaces. A graduated cylinder
contains 245.0 ml water. When a small piece of Pyrite, an ore
of Iron, is submerged in the water, the volume increases to
315.8 ml. What is the volume of the piece of Pyrite in cm3
and in liters.
Vol (ml) = 315.8 ml - 245.0 ml = 70.80 ml
Vol (cm3) = 70.80 ml x 1 cm3/ 1 ml = 70.80 cm3
Vol (liters) = 70.80 ml x 10 -3liters / ml = __________ liters
Archimedes Principle Problem
Problem: Calculate the density of an irregularly shaped metal
object that has a mass of 567.85 g if when it is placed into a
2.00 liter graduated cylinder containing 900.00 ml of water,
the final volume of the water in the cylinder is 1,277.56 ml?
Plan: Calculate the volume from the different volume
readings, and calculate the density using the mass that
was given.
Solution:
Volume = 1,277.56 ml - 900.00 ml = 377.56 ml
Density =
mass
volume
=
567.85 g
377.56 ml
= _________ g / ml
Definitions - Mass & Weight
Mass - The quantity of matter an object contains
kilogram - ( kg ) - the SI base unit of mass, is a
platinum - iridium cylinder kept in
Paris as a standard!
Weight - depends upon an object’s mass and the strength
of the gravitational field pulling on it.
A Sample Problem - I
International computer communications will soon be carried
by optical fibers in cables laid along the ocean floor. If one
strand of optical fiber weighs 1.19 x 10 -3 lbs/m, what is the
total mass (in kg) of a cable made of six strands of optical
fiber, each long enough to link New York and Paris?
(8.85 x 103 km).
Mass (kg) of Cable
Length (km) of Fiber
1 km = 103 m
Length (m) of Fiber
10 -3
2.205 lb = 1 kg
1m = 1.19 x
6 fibers = 1 cable
lb
Mass (lb) of Fiber
Mass (lb) of Cable
Sample Problem - II
Length (m) of Fiber = 8.85 x 103 km x 103m / km
= 8.85 x 106 m
Mass (lb) of Fiber = 8.85 x 106 m x 1.19 x 10-3 lb / 1m
= 1.05 x 104 lb
Mass (lb) of cable = 1.05 x 104 lb / 1 fiber x 6 fibers / 1 cable
= 6.30 x 104 lb / cable
Mass (kg) of cable = 6.30 x 104 lb / 1 cable x 1kg / 2.205 lb
= 2.86 x 104 kg / cable
A Problem on Density - I
Lithium (Li) is a soft, gray solid that has the lowest density
of any metal. If a slab of Li weighs 1.49 x 103mg and has
sides that measure 20.9 mm by 11.1 mm by 12.0 mm, what
is the density of Li in g/ cm3 ? Lengths (mm)
of sides
Mass (mg)
of Li
Lengths (cm)
of sides
Mass (g)
of Li
Volume (cm3)
Density (g/cm3) of Li
Density Problem - II
Mass (g) of Li = 1.49 x
103
mg x
1g
103 mg
= 1.49 g
Length (cm) of one side = 20.9 mm x 1cm / 10 mm = 2.09 cm
Similarly, the other side lengths are 1.11 cm and 1.20 cm
Volume (cm3) = 2.09 cm x 1.11 cm x 1.20 cm = 2.78 cm3
Density of Li =
1.49 g
2.78 cm3
= ___________ g/cm3
Like Problem on Density of a Metal
Problem: Cesium is the most reactive metal in the periodic
table, what is it’s density if a 3.4969 kg cube of Cs has sides
of 125.00 mm each?
Plan: Calculate the volume from the dimensions of the cube,
and calculate the density from the mass and volume.
Solution:
length = 125.00 mm = 12.500 cm
mass = 3.4969 kg x 1000g/kg = 3,496.9 g
Volume = (length)3 = (12.500 cm)3 = 1,953.125 cm3
density =
mass
volume
=
3496.9 g = _________g/ml
1,953.125 cm3
Temperature Scales and Interconversions
Kelvin ( K ) - The “Absolute temperature scale” begins at
absolute zero and only has positive values.
Celsius ( oC ) - The temperature scale used by science,
formally called centigrade and most
commonly used scale around the world,
water freezes at 0oC, and boils at 100oC.
Fahrenheit ( oF ) - Commonly used scale in America for
our weather reports, water freezes at 32oF,
and boils at 212oF.
Temperature Conversions
T (in K) = T (in 0C) + 273.15
T (in 0C) = T (in K) - 273.15
T (in 0F) = 9/5 T (in 0C) + 32
T (in 0C) = [ T (in 0F) - 32] 5/9
Temperature Conversions - I
The boiling point of Liquid Nitrogen is –1950C, what is the
temperature in Kelvin and degrees Fahrenheit?
T (in K) = T (in 0C) + 273.15
T (in K) = -195.8 0C + 273.15 = 77.35 K = ________ K
T (in 0F) = 9/5 T (in 0C) + 32
T (in 0F) = 9/5 ( -195.8 0C) + 32 = _______________ 0F
Temperature Conversions - II
The normal body temperature is 98.6 0F, what is it in
degrees Celsius and Kelvin?
T (in 0C) = [ T (in 0F) - 32] 5/9
T (in 0C) = [ 98.6 0F - 32] 5/9 = 37.0 0C
T (in K) = T (in 0C) + 273.15
T (in K) = 37.0 0C + 273.15 = _________ K
Rules for Determining Which Digits Are
Significant
All digits are significant, except zeros that are used only to
position the decimal point.
1. Make sure that the measured quantity has a decimal point.
2. Start at the left of the number and move right until you
reach the first nonzero digit.
3. Count that digit and every digit to it’s right as significant.
Zeros that end a number and lie either after or before the
decimal point are significant; thus 1.030 ml has four
significant figures, and 5300. L has four significant figures
also. Numbers such as 5300 L is assumed to only have 2
significant figures. A terminal decimal point is often used to
clarify the situation, but scientific notation is the best!
Examples of Significant Digits in Numbers
Number
- Sig digits
0.0050 L
two
18.00 g
four
0.00012 kg
two
83.0001 L
six
0.006002 g
four
875,000 oz
three
30,000 kg
one
5.0000 m3
five
23,001.00 lbs seven
0.000108 g
three
1,470,000 L
three
Number
-
1.34000 x 107 nm
5600 ng
87,000 L
78,002.3 ng
0.000007800 g
1.089 x 10 -6L
0.0000010048 oz
6.67000 kg
2.70879000 ml
1.0008000 kg
1,000,000,000 g
Sig digits
six
two
two
six
four
four
five
six
nine
eight
one
Rules for Significant Figures in Answers
1. For multiplication and division. The number with the
least certainty limits the certainty of the result. therefore, the
answer contains the same number of significant figures as
there are in the measurement with the fewest significant
figures. Multiply the following numbers:
9.2 cm x 6.8 cm x 0.3744 cm = 23.4225 cm3 = 23 cm3
2. For addition and subtraction. The answer has the same
number of decimal places as there are in the measurement
with the fewest decimal places. Example, adding two volumes
83.5 ml + 23.28 ml = 106.78 ml = 106.8 ml
Example subtracting two volumes:
865.9 ml - 2.8121393 ml = 863.0878607 ml = _______ ml
Rules for Rounding off Numbers:
1. If the digit removed is more than 5, the preceding number increases
by 1 : 5.379 rounds to 5.38 if three significant figures are retained and to
5.4 if two significant figures are retained.
2. If the digit removed is less than 5, the preceding number is
unchanged : 0.2413 rounds to 0.241 if three significant figures are
retained and to 0.24 if two significant figures are retained.
3.If the digit removed is 5, the preceding number increases by 1 if it is
odd and remains unchanged if it is even: 17.75 rounds to 17.8, but
17.65 rounds to 17.6. If the 5 is followed only by zeros, rule 3 is
followed; if the 5 is followed by nonzeros, rule 1 is followed:
17.6500 rounds to 17.6, but 17.6513 rounds to 17.7
4. Be sure to carry two or more additional significant figures through a
multistep calculation and round off only the final answer. (In sample
problems and follow-up problems, we round off intermediate steps of
a calculation to show the correct number of significant figures.)
Precision and Accuracy
Errors in Scientific Measurements
Precision - Refers to reproducibility or How close the
measurements are to each other!
Accuracy - Refers to how close a measurement is to the
real value!
Systematic error - produces values that are either all higher
or all lower than the actual value.
Random Error - in the absence of systematic error, produces
some values that are higher and some that
are lower than the actual value.