Transcript Chapter 1 Introduction Matter and Measurements

Introduction: Matter and
Measurement
SC 131 CHEM 1
Chemistry: The Central Science
CM Lamberty
Homework
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Chapter 1 Exercises (p 31-35)
12,
 36,
 42,
 56,
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14, 18, 20, 22, 24, 26, 28, 30, 32
40
46, 48a, 50, 52
58, 60, 62, 65, 68, 71, 72, 78
Chemistry
The study of materials and the changes
that materials undergoes
 Where is chemistry present in your life?
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The Study of Chemistry
The Atomic and Molecular Perspective
 Matter
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Property
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Anything with mass and occupies space
Characteristic that helps recognize a type of
matter and distinguish from other types
Elements
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100+ basic substances that make up matter
either alone or in various combinations
The Study of Chemistry
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Atom:
submicroscopic particles
 Fundamental building blocks
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Molecules
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Two or more atoms joined in specific geometric
arrangement
Bonds
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Electronic force that holds atoms together in
molecule
The Study of Chemistry

Why Study Chemistry?
Impacts daily lives
 Informs citizens
 Fulfills curriculum requirements
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Classification of Matter
Substance: specific instance of matter
 Solid: mq close and little movement
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Fixed volume, rigid shape
 Crystalline or amorphous
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Liquid: mq close but free to move
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Fixed volume, no fixed shape
Gas: mq far apart, compressible
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No fixed volume, no fixed shape
Classification of Matter
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Classification according to Composition
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Kinds and amt of substances that make up
matter
Pure substance: single type of atom/mq
Element—cannot be broken down further
 Compound—can be broken down into elements
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Fixed definite composition
Mixture
Heterogeneous
 Homogeneous
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Physical & Chemical Properties
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Physical Property—displays w/o changing
appearance
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Examples
Chemical Property—only displayed by
changing composition
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Examples
Physical & Chemical Changes
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Physical Change
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Alter only appearance
not composition
Ex
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Chemical Change
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Composition changes
Ex
Separation of Mixtures
Individual sorting by color or shape
 Use of physical properties
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Magnetic
 Filtration
 Distillation
 Chromatography
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Chemical reactivity
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One substance reacts while the other does not.
Need to be able to get back original substance.
The Scientific Approach to Knowledge
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Empirical
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Hypothesis
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Highly controlled experiments
reproducible
Theory
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Tentative explanation of observations
Experiments
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Observation and experimentation
Well-established hypotheses
Scientific Law
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Summarize past observations and predicts future ones
Units of Measurements
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International System of Units (SI)
Length
Mass
m
Kilogram
m
kg
Time
Second
s
Temperature
Kelvin
K
Amt of Subst
Mole
mol
Electric current
Ampere
A
Luminous intensity Candela
cd
Length and Mass
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Length
Meter
 Distance light (598 nm) travels in 1 second
 Just a bit more than a yard
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Mass
Amount of material in an object
 Not weight (which is a force)
 1 kg ~ 2.2 pounds
 Cube of Platinum in Sorbonne????
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Temperature
Hotness or coldness of an object
 Direction of heat flow
 Heat flows from higher T to lower T
spontaneously
 Celsius and Kelvin
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Kelvin is absolute scale and does not have
negative values
Conversion Factor
°F = 1.8(°C) + 32
 K = °C + 273.15
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Derived Units
Combination of other units
 Volume—amount of space matter occupies
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Vol of cube = (edge length)3
 Liter or milliliter (L or mL) for liquids
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Density—mass per unit volume
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Density = mass/volume = m/V
Intensive vs. Extensive Properties
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Intensive—independent of the amount of
substance
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Extensive—dependent upon the amount of
substance
Uncertainty in Measurement
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Precision vs. Accuracy
Precision is measure of how closely individual
measurements agree with one another
 Accuracy is how closely measurement agrees
with the correct or “true” value
 Perform several trials and average the results
 Standard deviation reflects how much results
differ from average
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Significant Figures
Uncertainty in Measurement
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Scientific measurements are
reported so that every digit is
certain except the last, which
is estimated.
Uncertainty in Measurement
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Significant Figures—only for measured
values
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The greater the number of significant figures,
the greater the certainty fo the measurement
Exact Numbers—actual counts
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No uncertainty, unlimited sig fig
Significant Figure Rules
All nonzero digits are significant
 Interior zeros are significant
 Leading zeros are not significant
 Trailing zeros
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After decimal point always significant
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Before decimal point are significant
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3.9000
40.00
Before implied decimal point are ambiguous
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1200
use sci notation 1.200 x 103 or 1.20 x 103
Significant Figures in Calculations
Multiplication/division—result uses fewest
number of sig fig
 Addition/subtraction—fewest number of
decimal places
 Rounding—4 or less round down, 5 or
greater round up
 Round at the end of all calculations not
individual steps
 Calculators are stupid & do not know rules
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Solving Chemical Problems
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Generally 2 types:
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Unit conversion (dimensional Analysis) or
specific equation
Dimensional Analysis
Calculate the displacement of a 5.70 L
automobile engine in cubic inches
Watch units raised to a power and account for that mathematically
General Problems Solving Strategy
Identify starting point (given info)
 Identify the end point (what you want)
 Devise a way to get from start to end—
conceptual plan
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Sort
 Strategize
 Solve
 Check
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