Transcript Metathesis Problems (and Some Solutions) Identified

Chem 1061
Principles of Chemistry I
Andy Aspaas, Instructor
About this class
• Prereq. to CHEM 1062
• More detail in underlying concepts than 1020
• Expected that you already have basic familiarity with
chemistry concepts
• Syllabus
Chapter 1
• Should be review, but still read carefully
• Why study chemistry?
– Practical applications
– Intellectual development
– Crossover to other fields
The scientific method
• Problem or question: what does the scientist wish to
accomplish in research?
• Law: a fundamental consistent observation
• Experimentation: controlled observations, aim is to
get consistent results that can be replicated and
explained
• Hypothesis: a tentative explanation
• Theory: a tested explanation
Matter and mass
• Matter is anything that occupies space
• Mass: a measure of the amount of matter in a
sample
– Only measured with a balance
• Weight: the gravitational force a sample exerts
– Measured with a scale
• Mass is always conserved in a chemical
transformation (reaction)
Physical states of matter
• Solid: rigid material; made of closely packed,
relatively motionless particles
• Liquid: mostly incompressible fluid; particles are in
close proximity but move freely
– (fluids flow easily and change shape to occupy
the space of their vessel)
• Gas: compressible fluid; particles are distant and
fast-moving
Changes
• Physical change: form of the matter is changed, but
not its chemical identity
– Phase changes: melting, freezing, boiling,
evaporation, condensation, sublimation
– Dissolving, like Kool-Aid into water
• Chemical change: matter is changed into a different
kind of matter
Types of matter
• Substances: cannot be separated into other types of
matter by physical processes
– Elements: cannot be decomposed into simpler
substances by chemical changes
– Compounds: composed of 2 or more chemically
combined elements
Types of matter
• Mixtures: can be separated by physical means into
other substances
– Heterogeneous: has parts with different
observable physical distinctions
– Homogeneous: uniform in properties throughout,
a.k.a. solutions
Physical measurements
• Measurement: comparison of physical quantity with
a fixed standard (a unit of measurement)
• Precision: how similar a number of measurements
are
• Accuracy: how close a single measurement is to its
true value
Significant figures
• The number of meaningful digits in a measurement,
indicating precision of measurement
– All nonzero digits are significant
– Zeroes at the beginning of a number are not
– Terminal zeroes are if there’s a decimal point
– Terminal zeroes with no decimal point usually are
not
– Exact quantities have an infinite number of sig
figs
Using sig figs
• x or ÷: answer has same number of sig figs as
measurement with least number of sig figs
• + or -: answer has same number of decimal places
as measurement with least number of decimal
places
• Exact numbers do not change number of sig figs or
decimal places in answer
• Round answer to give correct sig figs or decimal
places, do not round intermediate calcs
SI units
• Metric system uses SI units of measurement
– Easy conversions between units
– All decimal based
– Power of 10 prefix
SI base units
• Units from which all other SI units can be derived
Measurement
Unit
Length
meter
Mass
kilogram
Time
second
Temperature
kelvin
Quantity
mole
Electrical current ampere
Luminosity
candela
Symbol
m
kg
s
K
mol
A
cd
SI prefixes
Multiple
106
103
10-1
10-2
10-3
10-6
10-9
10-12
Prefix
mega
kilo
deci
centi
milli
micro
nano
pico
Symbol
M
k
d
c
m
µ
n
p
Length, mass, and time
• Meter (m) is SI base unit of length
– Nanometer (nm, 10-9 m) and Å (angstrom, 10-10
m) commonly used by chemists
• Kilogram (kg): mass, about 2.2 pounds
• Second (s): time - many of the fastest chemical
reactions are finished in picoseconds (10-12 s)
Temperature
• A measurement of the consequences of heat energy
on a substance
• Not a measurement of heat itself
• Celsius scale: most common scientific use
• Kelvin (K): SI base unit, lowest theoretical possible
temperature is zero (absolute zero)
• Fahrenheit scale: used in US
• Conversions
Derived units
• Obtained by mathematically combining 2 or more
other SI units
• Volume: length cubed. SI unit is m3
– Traditional unit is liter (L), equal to 1 dm3
– 1 milliliter (mL) = 1 cm3
• Density: mass per unit volume.
– Common unit is g/cm3
– Important characteristic of a substance
Dimensional analysis
• Systematic method of unit conversion
• Start with a single known quantity
• Multiply by conversion factors
– An equality written as a division of two units
– Arrange conversion factors so units cancel
– Unit of answer is apparent through calculation
– Estimate to make sure answer is reasonable