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Chem 140 Section AInstructor: Ken Marr
Weekly Schedule“Lecture” 9 -10, MWF in STB-2
“Lab” 8 -10 , Tu in STB-2
8 -10 , Th in STB-5
Chem 140 Section CInstructor: Ken Marr
Weekly Schedule“Lecture” 10 –11, MWF in STB-2
“Lab” 10-12 , Tu in STB-2
10-12 , Th in STB-5
Chem 140 Section EInstructor: Ken Marr
Weekly Schedule“Lecture” 1 - 2, MWF in STB-2
“Lab” 1 - 3 , Tu in STB-2
1 - 3 , Th in STB-5
Day 1 Activities Introduction to Course
» Briefly Review Course Outline/Syllabus Homework Assignments
» Reading: See Chem 140 schedule » Lab: Do Prelab assignment for the “Measurement and
Density” Lab» Stamped Assignment #1: Chapter 1 HW
– due Tues. 10/01/02 ……But start now!!!– Note: 10/2 is a very special day for your instructor!!
Begin Chapter 1» Alice 1 and 2
CHEMISTRY
The Study ofMatter and theChanges thatMatterUndergoes andThe EnergyAssociated withThe Changes
Chemistry
Oceanography Atmospheric Sciences
Economics
Engineering Physics Medicine
Governments
Geology
Anthropology
Biology
Astronomy
Politics
People
Chemistry as the Central Science
Chapter# 1 : Keys to the Study of Chemistry
1.1 Some Fundamental Definitions1.2 Chemical Arts and the Origins of Modern Chemistry1.3 The Scientific Approach: Developing a Model1.4 Chemical Problem Solving1.5 Measurement in Scientific Study1.6 Uncertainty in Measurement: Significant Figures
Measurement and Significant Figures
Measured Numbers are Never Exact...Why?» Which Graduated Cylinder is the most precise?» How is precision indicated when we record a
measurement?
The Number of Significant Figures in aMeasurement Depends Upon the
Measuring Device
Fig 1.14 3e
Significant Figures We use significant figures to indicate the
maximum precision of a measurement Significant Figures
»The number of digits that are known with certainty, plus one that is uncertain
»Significant figures are used only with measured quantities.
»Some numbers are exact and do not have any uncertainty......e.g...’s??
More Examples
Record the exact length in centimeters, cm (T2c)
Record the exact amounts for numbers 1-11 (T2d)
Sig. Fig. Rules to memorize.....(See page 27-30 Silberberg 3e)
1. All nonzero numbers are significante.g. 23.8 g, 2345 km, 11 mL, 5 inches
2. Zeros between nonzero digits are significant i.e. Sandwiched zeros are significant
e.g. 509 m, 2001 mL, 2050.1 L3. Zeros preceding the 1st nonzero digit are not
significant.......they serve only to locate the decimal point
e.g. 0.083 m, 0.000306 L– Try converting these numbers to Scientific Notation
to prove this!
More Sig. Fig. Rules Involving Zeros
4. Zeros at the end of number that include a decimal point are significant
» 0.800, 11.40, 10.00, 400.
5. Zeros at the end of a number without a decimal point are not significant... The Greenwater Rule!
» 40, 8800, 300, – Use of underlining and decimal points
Examples of Significant Digits in Numbers
Number - Sig digits Number - Sig digits
0.0050 L 1.34000 x 107 nm 0.00012 kg 87,000 L 83.0001 L 78,002.3 ng0.006002 g 0.000007800 g875,000 oz 1.089 x 10 -6L 30,000 kg 0.0000010048 oz 5.0000 m3 6.67000 kg23,001.00 lbs 2.70879000 ml 0.000108 g 1.0008000 kg 1,470,000 L 1,000,000,000 g
Rounding off Numbers Rounding off is used to drop non-significant
numbers» Rule 1
When the 1st digit after those you want to retain is 4 of less, that digit and all others to the right are dropped
Round off the following to 3 sig. figs.» 105.29, 189.49999, 1.003, 100.3, 1001
Rounding off Numbers Rule 2
When the 1st digit after those you want to retain is 5 or greater, that digit and all others to the right are dropped and the last digit retained is increased by one
Round off the following to 4 sig. figs.» 10.87519, 13.59800, 99.999, 1042.5
Sig. Figs. in Calculations
The Central Idea.....» The result of a calculation based on
measurements can not be more precise than the least precise measurement!
Some Rules to, yes, memorize......
Sig. Figs. in Multiplication and Division
“The Chain Rule”» Your answer must contain the same
number of sig figs as the measurement with the fewest sig figs.....Some e.g...’s...
(3.04) x (2.2) = 6.688 = ???
(2.00) / (0.3 ) = 6.666... = ???
(18.4) x (4.0) = 1.1117824 = ???
(66.2)
Sig. Figs. in Addition and Subtraction
“The Decimal Rule” » The answer must have the same precision
as the least precise measurement...or...– Your answer must be expressed to the same
number of decimal places as the measurement with the fewest decimal places.
The number of sig figs are not considered, only the number of decimal places are considered!!!
» Some examples..
Sig. Figs. in Addition and Subtraction
Examples.....» 12.89 + 12.1 + 11.803 + 19 = 55.793 = ?
» 1786 - 130 = 1656 = ???» 7331 + 0.495 = 7331.495 = ???
Scientific Notation
Scientific Notation» Writing a number as a number between 1
and 10 times a power of 10» WHY DO IT???
The Rules...
How to Write Numbers in Scientific Notation
1. Move the decimal point in the original number so that it is located after the first nonzero digit» e.g. 5682 ????
2. Multiply this number by the proper power of 10» The power of 10 is equal to the number of places the
decimal point was moved. POSITIVE IF MOVED TO THE LEFT NEGATIVE IF MOVED TO THE RIGHT
Examples.... Express the following numbers in scientific
notation...» 0.0421» 150,000» 5899
Express the following in “longhand” » 5.30 x 10-4
» 8.000 x 106
Meaning of Powers of 10
103 = 10-3 = 102 = 10-2 = 101 = 10-1 = 100 =
Metric System
System of measure built around standard or base units
Uses factors of 10 to express larger or smaller numbers of these units
Table 1. 2 (p. 17, 3e) SI - Base UnitsPhysical Quantity Unit Name Abbreviation
Mass Kilogram kg
Length meter m
Time second s
Temperature Kelvin K
Electric current ampere A
Amount of substance mole mol
Luminous intensity candela cd
Metric Base Units and their Abbreviations
Length Mass Volume Temperature
» Prefixes are added to these base units for quantities larger or smaller than the base unit
– Prefixes are a multiple of 10
Table 1.3 Common Decimal Prefixes Used with SI Units.
Prefix Prefix Number Word Exponential Symbol Notation
tera T 1,000,000,000,000 trillion 1012
giga G 1,000,000,000 billion 109
Mega M 1,000,000 million 106
Kilo k 1,000 thousand 103
hecto h 100 hundred 102
deka da 10 ten 101
----- ---- 1 one 100
deci d 0.1 tenth 10-1
centi c 0.01 hundredth 10-2
milli m 0.001 thousandth 10-3
micro millionth 10-6
nano n 0.000000001 billionth 10-9
pico p 0.000000000001 trillionth 10-12
femto f 0.000000000000001 quadrillionth 10-15
Common Metric Prefixes Memorize the Symbol, Numerical Value,
and Power of 10 Equivalent for.....» kilo-» centi-» milli-» micro-» nano-
Common Prefix Applications
Length: » km 1 km = ? m » cm 1 cm = ? m » mm 1 mm = ? m » µm 1 µm = ? m » nm 1 nm = ? m
Common Prefix Applications
Mass» kg 1 kg = ? g» mg 1 mg = ? g» µg 1 µg = ? g
Common Prefix Applications
Volume» mL 1 mL = ? L» µL 1 µL = ? L
Important Relationships Length
» 1 m = ?? cm » 1 m = ?? mm» 1 m = ?? µm» 1 cm = ?? mm
Important Relationships
Mass» 1 g = ?? mg» 1 kg = ?? g» 1 kg = ?? lb..
Some Volume Relationships in SI Units
Fig. 1.9
Important Relationships
Volume» 1 L = ?? mL » 1 mL = ?? cm3
» 1 L = ?? cm3
» 1 L = 1.057 qt.
Solving Chemistry ProblemsDevelop a Plan Carryout Plan Check Answer 1. Developing a Plan: Read the problem carefully!
• Clarify the know and unknown: What information is given? What are you trying to find?
• Think about how to solve the problem before you start to juggle numbers
Suggest steps from the known to unknown Determine principles involved and the relationships
needed Use sample problems as a guides
• Map out the strategy you will follow
Solving Chemistry Problems (cont.)
2. Solve the problem: Carry out your plan» Set up problem in a neat, organized, and logical
way!» Unwanted units should cancel to give the desired
unit of measure» Make a rough estimate of the answer before
using your calculator» Round off to correct number of sig. figs.» Answer must have correct units
Solving Chemistry Problems (cont.)
3. Check your answer» Is it reasonable?» Correct nits? » Same “ballpark” as a rough estimate? » Makes chemical sense?
Problem Solving: Some Examples
1. How many hours would it take a pump to remove the water from a flooded basement that is about 30 feet wide and 50 feet long with water at a depth of about 2 feet? The pump has a capacity of 80 liters per minute. See Table 1.4, Common SI-English Equivalent Quantities, page 18 Silberberg 3e.
1062 min = 17.7 hours = 20 hours
Metric Conversion Factors
Be able to do conversions within the metric system involving the common metric prefixes» kilo-» centi-» milli-» micro-» nano-
– e.g. #32 on page 43
Metric - English Conversions
Given metric - English conversion factors, be able to convert between these two systems
You do not have to memorize metric to English conversions factors
Measurement of Temperature
Heat vs. Temperature» Temperature (SI unit: Kelvin, K)
– A measure of how hot or cold an object is relative to another object
– Also measured in degrees Celsius, oC
» Heat (SI unit: joule, J)– The energy transferred between objects at different
temperatures– A form of energy associated with the motion of atoms
and molecules (the small particles of matter)– Also measured in calories, cal
Application: Heat vs. Temperature
Which contains more heat...» 1 mL of water at 90 oC or 1 liter of water at
90 oC ?» 1 burning match or 10 burning matches?
Temperature Conversions
The boiling point of Liquid Nitrogen is - 195.8 oC, what is the temperature in Kelvin and degrees Fahrenheit?
T (in K) = T (in oC) + 273.15T (in K) = -195.8 + 273.15 = 77.35 K = 77.4 K
T (in oF) = 9/5 T (in oC) + 32T (in oF) = 9/5 ( -195.8oC) +32 = -320.4 oF
The normal body temperature is 98.6oF, what is it in Kelvinand degrees Celsius?T (in oC) = [ T (in oF) - 32] 5/9T (in oC) = [ 98.6oF - 32] 5/9 = 37.0 oC
T (in K) = T (in oC) + 273.15T (in K) = 37.0 oC + 273.15 = 310.2
Density Density = mass (g) / Volume (mL or cm3 or L)
» Physical characteristic of a substance» Aids in identification of a substance» Calculated by.....
– divide the mass of a substance by the volume occupied by that mass
– Units mass in grams volume
» Solids and Liquids: mL or cm3
» Gasses: L
Density
Densities vary with temperature!» Why??
Would you expect densities to increase or decrease as the temperature increases?
Density Immiscible liquids and solids separate into
layers according to their densities» List the order from top to bottom when the following
are mixed– Hg (13.5525 g/mL) – Carbon Tetrachloride (1.59525 g/mL)– Mg (1.7425 g/mL)– Water (1.004 g/mL)
What do the superscripts mean next to each density listed above?
Calculations Involving Density Be able to calculate the density, mass, or
volume of a substance » Use the plug and chug method or use density as a
conversion factor Practice makes perfect....
Specific Gravity Compares the density of a liquid or solid to that
of water... Units???» Sp. Gravity = dsolid or liquid / dwater
– Usually use dwater @ 4oC = 1.000g/mL
Compares the density of a gas to that of air...... Units???» Sp. Gravity = dgas/ dair
Mass vs. Weight
Mass» Amount of matter in an object» Independent of location» Measure with a balance by comparison with
other known masses
Mass vs. Weight
Weight» Measures earth’s gravitational attraction on
an object» Measure with a scale
– measures force against a spring
» Depends on– position relative to earth– motion of object w.r.t. the earth
Scientific Approach: Developing a Model
Observations : Natural phenomena and measured events; universally consistent ones can be stated as a natural law.
Hypothesis: Tentative proposal that explains observations.
Experiment: Procedure to test hypothesis; measures one variable at a time.
Model (Theory): Set of conceptual assumptions that explains data from accumulated experiments; predicts related phenomena.
Further Experiment: Tests predictions based on model.