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Chapter 1
Introduction
Why Learn Chemistry?
To better understand the environment around us
Medicine
Understanding disease
Develop new drugs
Environmental Science
Ozone layer
Global warming
Acid rain
Agriculture
Bioengineered food
Fertilizers
Criminal Justice
Forensics
Material Science
Better built houses
More efficient cars
Plastics, composites
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Learning the Language
Chemistry defines materials and predicts
molecular reactions based on 3 concepts
Composition
Mass percent of molecules present
Molecular ratios within material
Stoichiometry
Structure
Molecular arrangement
Phase: s, l, g
Properties
Specific to a particular material
(boiling point, color, odor, reactivity)
Used for identification
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The Scientific Method
Series of steps that explain an observation
Define the
problem
A balloon pops
if overheated
Perform
Develop
hypothesis
experiments
Gas expands
when heated
experiments
Perform
Experiments
Heat balloon and
observe V change
Support or refute
hypothesis
Quantitatively
measure ∆V vs. ∆T.
Develop
scientific laws
Charles’ Law:
V1/T1 =V2/T2
Develop
theory
Kinetic Molecular
Theory
Perform
Molecules move faster when heated requiring more
space, causing balloon to pop.
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Classifications of Matter
What is in the material you are
investigating?
Pure materials
Atom:
Smallest distinctive unit
Molecule:
2 or more atoms together
Substance:
Group of identical molecules
Element: atoms identical
Compound: atoms vary
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Mixtures
Mixture: Combination of 2 or more substances
Homogeneous Mixture
Substances stay mixed
No distinct layers
Also called a “solution”
14 karat gold
Mixture of gold and silver
Heterogeneous Mixture
Substances separate
Distinct layers often seen
Iron filings and sand
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Matter Summary
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Physical and Chemical
Properties of Matter
Means of identification & separation
of substances
Physical Properties of Matter
No change to molecular composition
All changes are at the substance level
eg: smashing a window, melting ice
Phase changes: solid to liquid to gas etc.
Melting, freezing, boiling, etc.
ID a substance without damage
Color, odor, solubility, conductivity
molecular mass, density, boiling/melting points
Original compound can be recovered
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Chemical Properties of Matter
All chemical reactions
Heat or light generated: Burning, explosions
Decomposing:Rusting, rotting
Compositional changes to molecules
Often called a chemical change
Original material changed on an atomic level
Molecules of original compound no longer present
Compound cannot be restored to its original form without
another chemical change
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Extensive and Intensive Properties
Extensive Property: Varies on amount of matter present
mass, length, volume, heat,
intensity of color or odor
Intensive Property: Independent of amount of matter present
Temperature, boiling point, color, odor
Often a calculated ratio
Density (mass/vol ratio)
Molar mass Specific heat
Can be used to identify a material
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Measurements
Determining how much
matter is present
Base Units of Measurement
International System of Units (SI)
Memorize Chart!
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SI Base Prefixes
Memorize Chart!
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Volume
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SI derived unit for volume is a cubic meter (m3)
Common unit is a “Liter (L)”
1L = 1000cm3 =
1m
1m
1m
1000cm 1cm 1cm
x
x
x
x
x
= 1x10 −3 m 3
1 100cm 100cm 100cm
1
1
1cm
1cm
1 mL = 1 cm3
1cm
Density
Density: Ratio of mass to volume of a material
density =
mass
volume =
m
V
SI derived unit for density is kg/m3
1 g/cm3 = 1 g/mL = 1000 kg/m3
Intensive property
Can be used to identify a material
Units of mass and volume may vary
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Handling Numbers
Math Review
Scientific Notation
Displaying very large or small numbers
1700000 → 1.7 x 106
0.0000017 → 1.7 x 10-6
2 parts: significant values & a multiplier
Significant:
Multiplier:
17 for both values
100000 or 0.000001
Keep all significant numbers
Place decimal after 1st significant figure (1.7)
Multiplier used as exponent: 10 x or 10 -x
1700000 =1.7x 106
0.0000017 =1.7x10-6
Use EXP, SCI or EE keys on calculator
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Significant Figures:
Number of Digits in Final Answer
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1. All non-zero digits are significant
2. Use decimal point to determine significance of zeros
Between 2 numbers
significant
50.002
Before decimal point
not significant
0.502
Before the first digit
not significant
0.0052
End of # after decimal significant
0.0200
No decimal point:
can’t tell
500
3. Exact numbers have unlimited number of significant figures
Inherently an integer:
4 sides to a square
Inherently a fraction:
½ of a pie
Obtained by counting: 47 people in a class
Defined quantity:
12 eggs in a dozen
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3
2
3
?
Determine the correct number of significant figures
(2.45 + 0.26800) x 3.575 = 9.71685
Addition/subtraction
(12.45 + 9.2680 ) = 3.182
2 sigfigs after decimal
3 sigfigs overall in final answer
Sigfigs based on decimal
12.45XX
- 9.2680
3.1820
Multiplication/Division
Use all significant digits
Rounding
Based on number after sigfigs
3.182 x 3.575 = 9.71685
9.71685 = 9.72
round up 6>5
3 sigfigs in final answer
Addition limits sigfigs
If < 5 Use number as written
If ≥ 5 Round up 1 digit
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Precision and Accuracy
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Accuracy – how close a measurement is to the true value
Precision – how close measurements are to each other
accurate
&
precise
precise
but
not accurate
not accurate
&
not precise
Percent Error
Comparison of experimental results to expected or real values
Usually reported without a + or - sign
Deviation
% error = Deviation x 100
Real value
Experimental value - real value
Often reported with a + or – sign
Real value:
Widely accepted, often an industry standard value
Average of several experiments if real value unknown
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Dimensional Analysis
Algebra and canceling units
Look at question:
How many kilograms of methanol will fill a 15.5 gallon fuel
tank of a car modified to run on methanol?
What unit do you want to solve for: kilograms (kg)
What information do you need?
Data in problem:
Data to look up:
Data to know:
Volume = 15.5 gallons
Density of methanol= 0.791 g / mL
Gallon to Liter conversion: 1gal= 3.785L
1000mL = 1L
1000g = 1kg
kg 0.791g 1kg 1000mL 3.785 L 15.5 gal
x
x
=
x
x
= 46.4kg
L
1
1ml
1000 g
1gal
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