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Introduction: Matter and
Measurement
SC 131 CHEM 1 Chemistry: The Central Science
CM Lamberty
Homework Chapter 1 Exercises (p 31-35)
12, 14, 18, 20, 22, 24, 26, 28, 30, 32 36, 40 42, 46, 48a, 50, 52 56, 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
Anything with mass and occupies space Property
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
Observation and experimentation Hypothesis
Tentative explanation of observations Experiments
Highly controlled experiments reproducible
Theory Well-established hypotheses
Scientific Law Summarize past observations and predicts future ones
Units of Measurements International System of Units (SI)
Length m m
Mass Kilogram 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 3.9000
Before decimal point are significant 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