chem 100 fall 2014 la tech instructor: dr. upali siriwardane e-mail: [email protected] office: cth...
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CHEM 100 Fall 2014 LA Tech
Instructor: Dr. Upali Siriwardanee-mail: [email protected]: CTH 311 Phone 257-4941Office Hours: M,W, 8:00-9:30 & 11:30-12:30 a.m Tu,Th,F 8:00 - 10:00 a.m. Or by appointmentTest Dates:
Chemistry 100(02) Fall 2014
September 29, 2014 (Test 1): Chapter 1 & 2 October 20, 2014 (Test 2): Chapter 3 & 4 November 12, 2014 (Test 3) Chapter 5 & 6November 13, 2014 (Make-up test) comprehensive: Chapters 1-6 9:30-10:45:15 AM, CTH 328
REQUIRED :Textbook: Principles of Chemistry: A Molecular Approach, 2nd Edition-Nivaldo J. Tro - Pearson Prentice Hall and also purchase the Mastering Chemistry Group Homework, Slides and Exam review guides and sample exam questions are available online: http://moodle.latech.edu/ and follow the course information links.OPTIONAL : Study Guide: Chemistry: A Molecular Approach, 2nd Edition-Nivaldo J. Tro 2nd EditionStudent Solutions Manual: Chemistry: A Molecular Approach, 2nd Edition-Nivaldo J. Tro 2nd
Text Book & Resources
CHEM 100 Fall 2014 LA Tech
Chapter 1. Matter, Measurement, and Problem Solving
1. 1 Atoms and Molecules………………………………….. 11 .2 The Scientific Approach to Knowledge…………….. 31 .3 The Classification of Matter…………………………… 51 .4 Physical and Chemical Changes and Physical and Chemical Properties…………………………………….. 91 .5 Energy: A Fundamental Part of Physical and Chemical Change…………………………………………………….. 121 .6 The Units of Measurement……………………………... 131 .7 The Reliability of a Measurement……………………… 201 .8 Solving Chemical Problems……………………………. 27
CHEM 100 Fall 2014 LA Tech
Chapter 1. KEY CONCEPTS
• What is chemistry?• Scientific Method.• Properties of the three states of
matter• Physical changes and
properties.• Chemical change and
properties.• Categories of matter. • Elements and Compounds• Atomic symbols• Chemical Elements and
properties• Chemical Symbolism• Separating Mixtures.• Scientific Measurement
• Prefixes of SI units• Macro, micro and nano-scales • Conversion factors.• Factor label method.• Uncertainty and significant
figures• Temperature Conversions.• Density Calculations.• Three chemical Laws• Dalton's atomic theory • Interpreting chemical formulas
and chemical reaction.• Concept of mole• Gram to mole conversion
CHEM 100 Fall 2014 LA Tech
Units
CHEM 100 Fall 2014 LA Tech
Length meter (m)
SI UNITS OF MEASUREMENT
Mass kilogram (kg)
Time second (s)
Temperature kelvin (K)
Amount mole (mol)
6.02 x 1023 units
Five Basic Units
CHEM 100 Fall 2014 LA Tech
The Units of Measurement
1) Give the name and abbreviation of the SI Unit for:
a) Length b) Mass c) Time
d) Amount of substance e) Temperature
CHEM 100 Fall 2014 LA Tech
Prefix SymbolDecimal
EquivalentPower of 10
mega- M 1,000,000 Base x 106
kilo- k 1,000 Base x 103
deci- d 0.1 Base x 10−1
centi- c 0.01 Base x 10−2
milli- m 0.001 Base x 10−3
micro- m or mc 0.000 001 Base x 10−6
nano- n 0.000 000 001 Base x 10−9
pico p 0.000 000 000 001 Base x 10−12
Metric SystemHow to change measurements to reasonable numbers
CHEM 100 Fall 2014 LA Tech
Macroscale, Microscale, and Nanoscale
CHEM 100 Fall 2014 LA Tech
2) Give the abbreviation for the following units and describe what they are used to measure:
a) cubic centimeter b) micrometer
c) nanoseconds d) millimole
CHEM 100 Fall 2014 LA Tech
3) Give the name and the abbreviation (without looking in the book) of the SI or metric prefix for:
a) 10-12 b) 106 c) 10-9 d) 10-2
e) 10-3 f) 109 g) 103 i) 10-6
CHEM 100 Fall 2014 LA Tech12
Uncertainty in a Measurement
• The last digit is an estimate.
• .Measurement ≈ 26.13 cm
types of errors, random and systematic.
Careless measurementsLow resolution instrumentsCalibration errors
CHEM 100 Fall 2014 LA Tech
Uncertainty and Significant Figures
All measurements involve some uncertainty.
Scientists write down all the digits that have no uncertainty plus one additional uncertain digit.
If an object is reported to have a mass = 6.3492 g, the last digit (“2”) is uncertain ( it is probably close to 2, but may be 4, 1 … etc).
There are five significant figures in this number. All the digits are meaningful.
CHEM 100 Fall 2014 LA Tech
Uncertainty and Significant Figures
To find the number of significant figures:
Read a number from left to right and count all digits, starting with the first non-zero digit.
All digits are significant except those zeros that are used to position a decimal point (“placeholders”).
0.00034050
5 sig. figs.
Scientific Notation (3.4050 x 10-4)
placeholders
significant
significant
CHEM 100 Fall 2014 LA Tech
• All non-zero digits are significant.– Example: 536 has three significant figures.
• Zeros between non-zero digits are also significant.– Example: 6703 has four significant figures.
• Place holder zeros:– Zeros to the left of a non-zero digit are NOT significant.
• Example: 0.0043 has two significant figures.• Example: 0.0600 has three significant figures.
– Zeros to the right or after a non-zero digit to the decimal point are NOT significant.• Example: 7000 has only one significant figure.• Example: 32040 has four significant figures.• Example: 50.0 has three significant figures; all the
zeros are significant.
Significant Figure Primer
CHEM 100 Fall 2014 LA Tech
Uncertainty and Significant Figures
Number Sig. figs. Comment
2.12 3
4.500 4 The zeros are not placeholders. They are significant.
0.002541 4 The zeros are placeholders (not significant).
0.00100 3 Only the last two zeros are significant.
500 1, 2, 3 ? Ambiguous. If a number lacks a decimal point the zeros may be placeholders or may be significant.
500. 3 Adding a decimal point is one way to show that the zeros are significant.
5.0 x 102 2 No ambiguity.
Examples
CHEM 100 Fall 2014 LA Tech
The Reliability of a Measurement
4) Express the following numbers in scientific notation with the appropriate number of significant figures:
a) 10980000000 b) 414100
c) 0.000095162 d) 746.5 x 107
CHEM 100 Fall 2014 LA Tech
Consider rounding 37.663147 to 3 significant figures.
RoundingLook at the 1st non-significant digit (the digit after the last one retained). If it:
is > 5, round the last retained digit up by 1.
is < 5, make no change.
equals 5, and the 2nd non-significant digit is:absent, round the last retained digit up by 1.
odd, round the last retained digit up by 1.
even, make no change.
last retained digit
1st non-significant digit
It rounds up to 37.7
2nd non-significant digit
CHEM 100 Fall 2014 LA Tech
RoundingExamplesRound the following numbers to 3 significant figures:
1st non-sig. 2nd non-sig.Rounded
Number digit digit Number
2.123 2.123 - 2.12
51.372 51.372 51.372 51.4
131.5 131.5 - 132.
24.752 24.752 24.752 24.7
24.751 24.751 24.751 24.8
0.06744 0.06744 - 0.0674
CHEM 100 Fall 2014 LA Tech
Can you define accuracy vs. precision?
Precision = the degree of exactness of a measurement that is repeatedly recorded.Accuracy = the extent to which a measured value agrees with a standard value• Which set is more precise?
18.2 , 18.4 , 18.3517.9 , 18.3 , 18.8516.8 , 17.2 , 19.44
CHEM 100 Fall 2014 LA Tech
Three targets with three arrows each to shoot.
Can you hit the bull's-eye?
Both accurate and precise
Precise but not accurate
Neither accurate nor precise
How do they compare?
CHEM 100 Fall 2014 LA Tech
Speed of light is 3.00 x 108 m s-1 . Convert the speed of light to miles per year (1 mile = 1.61 km).
Unit Conversion Calculation
CHEM 100 Fall 2014 LA Tech
Using Conversion Factors
5) Convert 78.01 inches into:
a) feet b) meters
6) Convert 15.42 meters into:
a) kilometers b) micrometers
CHEM 100 Fall 2014 LA Tech
Example: 301 in scientific notation is 3.01 x 102.NOTE: The decimal point was moved two
places to the left.
Example: 0.0301 in scientific notation is 3.01 x 10-2. NOTE: The decimal point was moved two
places to the right.
Both of these value indicate THREE significant figures.
Significant Figures and Scientific Notation
CHEM 100 Fall 2014 LA Tech
adp = 4adp = 3
Significant Figures in Add/Sub
The answer you report in a problem should only include significant digits.Addition and subtraction
Find the number of digits after the decimal point (adp) in each number.
answer adp = smallest input adp.
Example
Add: 17.245 + 0.1001 17.3451 Rounds to: 17.345 (adp = 3)
CHEM 100 Fall 2014 LA Tech
Examples: 2 3 .4 6 7 in + 3 1 3 .2 1 in 3 3 6 .6 7 7 in but you would report
336.68 in
4 5 7 cm - 0 . 6 8 cm
4 5 6 . 3 2 cm but you would report 456 cm
Addition and Subtractions Examples:
CHEM 100 Fall 2014 LA Tech
Significant Figures Add/Sub
adp = 2adp = 4
Example
Subtract 6.72 x 10-1 from 5.00 x 101
Write the numbers down with the same power of 10:
5.00 x 101
– 0.0672 x 101
4.9328 x 101
Rounds to: 4.93 x 101 adp = 2
CHEM 100 Fall 2014 LA Tech
sig. fig. = 4sig. fig. = 5
Significant Figures Mul/Div
Multiplication and DivisionFind the number of significant figures (sig. fig.) in each number.
Answer has sig. fig = smallest input sig. fig.
Example
Multiply 17.425 and 0.100117.245
x 0.1001 1.7262245
Rounds to: 1.726 sig. fig. = 4 ExampleMultiply 2.346 x 12.1 x 500.99
Rounds to: 1.42 x 104 (3 sig. fig.)
= 14,221.402734
CHEM 100 Fall 2014 LA Tech
7) Perform the following calculations and give the answer in the correct number of significant figures. a) 30.84 + 9.74 Answer:
Scientific notation:
b) 30.84 + 9.74486 Answer: Scientific notation:
c) 145 + 1.54 x 10-6 Answer: Scientific notation:
CHEM 100 Fall 2014 LA Tech
7) Perform the following calculations and give the answer in the correct number of significant figures.
2 adp 2 adp 2 adp
a) 30.84 + 9.74 Answer: 40.58 Scientific notation: 4.058 x 101
2 adp 5 adp 2 adp
b) 30.84 + 9.74486 Answer: 40.58486 Scientific notation: 4.058 x 101
0 adp 8 adp 0 adp
c) 145 + 1.54 x 10-6 Answer: 145.00000154 Scientific notation: 1.45 x 102
CHEM 100 Fall 2014 LA Tech
7) Perform the following calculations and give the answer in the correct number of significant figures. d) 40.79 - 1.18432 Answer: Scientific notation:
e) 1.43 x 0.848 Answer: Scientific notation:
f) (7.601x107) x (8.09x10-4) Answer
Scientific notation:
CHEM 100 Fall 2014 LA Tech
7) Perform the following calculations and give the answer in the correct number of significant figures.
2 adp 5 adp 2 adpd) 40.79 - 1.18432 Answer: 41.97432 Scientific notation: 4.197 x 101
Multiplication
3 sfg 3 sfg 3 sfg
e) 1.43 x 0.848 Answer: 1.21264 Scientific notation: : 1.21 x 100 = 1.21
4 sfg 3 sfg 3 sfg
f) (7.601x107) x (8.09x10-4) Answer 61492.09 =615
Scientific notation: 6.15 x 102
CHEM 100 Fall 2014 LA Tech
Temperature Scales: Comparison
CHEM 100 Fall 2014 LA Tech
Temperature Conversions
Human body temperature is 98.6 oF. Convert this temperature to oC and K scale
oC = 5/9 (98.6 - 32) = 5/9 (66.6) = 37.0
oC--> K = 37.0 oC +273.15 = 310.2 K
Shift the scale to zero
Convert the scale 100/180
Shift the scale to zero K
CHEM 100 Fall 2014 LA Tech
Temperature ConvesionsoF -- > oC ; C = 5/9 (F - 32)oC -- > oF ; F =9/5 C + 32oC -- > K ; K = C + 273.15
8) Convert 98.6 °F into:
a) °C b) K.
CHEM 100 Fall 2014 LA Tech
Problem Solving by Factor Label Method
– State question in mathematical form– Set equal to piece of data specific to the problem– Use conversion factors to convert units of data
specific to problem to units sought in answer– Other names used Unit Conversion Method
or dimensional (Unit) Analysis
CHEM 100 Fall 2014 LA Tech
Common Conversion Factors
Length 1 kilometer = 1000 m = 0.62137 mile1 inch = 2.54 cm (exactly)1 angstrom (Å) = 1 x 10-10 m
Volume 1 liter (L) = 1 x 10-3 m3
= 1000 cm3 = 1000 mL= 1.056710 quarts
1 gallon = 4 quarts = 8 pints
Mass1 amu = 1.6606 x 10-24 g1 pound = 453.59237 g = 16 ounces1 ton (metric) = 1000 kg1 ton (US) = 2000 pounds
CHEM 100 Fall 2014 LA Tech
Solving Chemical Problems 9) Convert 75 miles per hour into: m s-1.
CHEM 100 Fall 2014 LA Tech
Solving Chemical Problems 10) Convert 100 m2 into cm2
11) Convert 1 m3 into cm3
.
CHEM 100 Fall 2014 LA Tech
Mathematical operations dictate the reporting of significant figures in an answer.
1. Multiplication and Division
The least precise measured value determines the number of significant figures in the reported answers.
2. Addition and Subtraction
The value with the smallest decimal measurement determines the answer’s significant figure.
Significant Figures andMathematical Operations
CHEM 100 Fall 2014 LA Tech
Solving Chemical Problems
13) Perform the following mathematical operations and give the answer with the correct number of significant figures
a) (2.481 x 12.74) + 0.27=
2.69
b) (4.73 x 10-4) - (72.85) =
(872.3) - (0.305)
:
CHEM 100 Fall 2014 LA Tech
Density = mass (g)
volume (cm3) An INTENSIVE physical property
The physical property does not depend on amount of substance.
The physical properties of mass and volume that determine a substance’s density are EXTENSIVE.Extensive physical properties are dependent on amount. Densities of liquid and gases are affected by temperature.
Density
CHEM 100 Fall 2014 LA Tech
PROBLEM:
Mercury (Hg) has a density of 13.6 g/cm3. What is the mass of 95 mL of Hg in grams? In pounds?
Strategy:1. Convert mL to cm3.2. Solve for mass (in grams) using density relationship.3. Convert grams to pounds.
Density Calculations
CHEM 100 Fall 2014 LA Tech
PROBLEM: Mercury (Hg) has a density of 13.6 g/cm3. What is the mass of 95 mL of Hg in grams? In pounds?
Density = mass (g)volume (cm3)
Step 1: 95 mL x (1cm3/1mL) = 95 cm3
Step 2: 13.6 g/cm3 = x / 95 cm3
x = 1.29 x 103 g, but report 1.3 x 103 g
Step 3: 1.3 x 103 g x (1 lb/454 g) = 2.9 lb
A Density Calculation
CHEM 100 Fall 2014 LA Tech
Solving Chemical Problems 12) Aluminum block weighs 14.2 g and has a density of
2.70 g cm-3. Calculate the volume of the block.
CHEM 100 Fall 2014 LA Tech
Problem:
The density of octane (C8H18) is 7.00 lb/gal.a) What is density in mg/cm3?b) What is the mass in grams of 1.25 liters of octane?
Strategy:1. Convert 7.00 lbs to mg.2. Change gallons to cm3.3. Determine the density of octane in mg/cm3.4. Convert 1.25 L to mL.5. Determine the mass of octane in 1.25 L using density.