Chapter 1 Introduction Matter and Measurements
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Transcript Chapter 1 Introduction Matter and Measurements
Introduction: Matter and
Measurement
SC 131 CHEM 1
Chemistry: The Central Science
CM Lamberty
Homework
Chapter 1 Exercises (p 31-35)
12,
36,
42,
56,
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?
The Study of Chemistry
The Atomic and Molecular Perspective
Matter
Property
Anything with mass and occupies space
Characteristic that helps recognize a type of
matter and distinguish from other types
Elements
100+ basic substances that make up matter
either alone or in various combinations
The Study of Chemistry
Atom:
submicroscopic particles
Fundamental building blocks
Molecules
Two or more atoms joined in specific geometric
arrangement
Bonds
Electronic force that holds atoms together in
molecule
The Study of Chemistry
Why Study Chemistry?
Impacts daily lives
Informs citizens
Fulfills curriculum requirements
Classification of Matter
Substance: specific instance of matter
Solid: mq close and little movement
Fixed volume, rigid shape
Crystalline or amorphous
Liquid: mq close but free to move
Fixed volume, no fixed shape
Gas: mq far apart, compressible
No fixed volume, no fixed shape
Classification of Matter
Classification according to Composition
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
Fixed definite composition
Mixture
Heterogeneous
Homogeneous
Physical & Chemical Properties
Physical Property—displays w/o changing
appearance
Examples
Chemical Property—only displayed by
changing composition
Examples
Physical & Chemical Changes
Physical Change
Alter only appearance
not composition
Ex
Chemical Change
Composition changes
Ex
Separation of Mixtures
Individual sorting by color or shape
Use of physical properties
Magnetic
Filtration
Distillation
Chromatography
Chemical reactivity
One substance reacts while the other does not.
Need to be able to get back original substance.
The Scientific Approach to Knowledge
Empirical
Hypothesis
Highly controlled experiments
reproducible
Theory
Tentative explanation of observations
Experiments
Observation and experimentation
Well-established hypotheses
Scientific Law
Summarize past observations and predicts future ones
Units of Measurements
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
Length
Meter
Distance light (598 nm) travels in 1 second
Just a bit more than a yard
Mass
Amount of material in an object
Not weight (which is a force)
1 kg ~ 2.2 pounds
Cube of Platinum in Sorbonne????
Temperature
Hotness or coldness of an object
Direction of heat flow
Heat flows from higher T to lower T
spontaneously
Celsius and Kelvin
Kelvin is absolute scale and does not have
negative values
Conversion Factor
°F = 1.8(°C) + 32
K = °C + 273.15
Derived Units
Combination of other units
Volume—amount of space matter occupies
Vol of cube = (edge length)3
Liter or milliliter (L or mL) for liquids
Density—mass per unit volume
Density = mass/volume = m/V
Intensive vs. Extensive Properties
Intensive—independent of the amount of
substance
Extensive—dependent upon the amount of
substance
Uncertainty in Measurement
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
Significant Figures
Uncertainty in Measurement
Scientific measurements are
reported so that every digit is
certain except the last, which
is estimated.
Uncertainty in Measurement
Significant Figures—only for measured
values
The greater the number of significant figures,
the greater the certainty fo the measurement
Exact Numbers—actual counts
No uncertainty, unlimited sig fig
Significant Figure Rules
All nonzero digits are significant
Interior zeros are significant
Leading zeros are not significant
Trailing zeros
After decimal point always significant
Before decimal point are significant
3.9000
40.00
Before implied decimal point are ambiguous
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
Solving Chemical Problems
Generally 2 types:
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
Sort
Strategize
Solve
Check