Transcript Chapter 1 Chemical Foundations - macroscopic world – objects we observe directly - cars, baseballs, planets, grains of sand, … - microscopic world.

Chapter 1
Chemical Foundations
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- macroscopic world – objects we observe directly
- cars, baseballs, planets, grains of sand, …
- microscopic world – objects we observe indirectly
or with the aid of instruments
- atoms, molecules, bacteria, viruses,…
- we are going to study the microscopic(atoms and
molecules) as a way of understanding the
macroscopic(solids, liquids, gases,…)
- Chemistry – science of materials,
composition and structure and the changes
the materials will undergo.
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1.2 - The Scientific Method
1. Observations
• quantitative – measurements(#’s and units)
• qualitative – descriptive(dilute, strong, weak, hot,
cold)
2. Formulate hypotheses
•
possible explanation for the observation
3. Performing experiments
•
gathering new information to decide whether the
hypothesis is valid
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Outcomes Over the Long-Term
Theory (Model)
 An explanation of why nature behaves in a
particular way.
•
•
•
proved through numerous observations and experiments
continually revised
true
•
Phlogiston theory
Natural Law
 A summary of what happens or a statement of
fact
•
•
does not explain how or why
Example - Law of Conservation of Mass
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Law vs. Theory
A law summarizes what happens;
A theory (model) is an explanation
why/how it happens.
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(1) Collect data.
(2) Analyze the data, looking for a trend. (If found, the
trend is a "Natural Law*.")
(3) Hypothesize a reason for the trend.
(4) Test the hypothesis. If it fails, repeat (3) as many times
as necessary.
(5) If the scientific community agrees, the hypothesis is
accepted as a theory (with your name on it, if you are
lucky).
*A Natural Law does not need an explanation. You can
create a cuckoo clock driven by a falling weight without
knowing anything about Newton's Theory of
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Gravitation.
1.3 - Units of Measurement
Measurement - quantitative observation consisting of
2 parts
Part 1 - number
Part 2 - scale (unit)
Examples:
20 grams
6.63   Joule seconds
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International System(le Système International)
or
SI measurements
• Based on metric system and units
derived from metric system.
• U.S. only industrialized nation that
still uses the antiquated and ridiculous
English system
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Jerseylicious video
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measuring fractions w/ OCC
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Copyright©2000 by Houghton
Mifflin Company. All rights reserved.
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The Fundamental SI Units
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derived units
• units derived mathematically from other
measurements
• not SI fundamental units
• volume – derived from length (V = l x w x h)
• liter( L) = (10cm)3
• 1 cm3 = 1 mL
• density – derived from mass and volume (D =
mass/vol) - g/L or g/mL
• speed – derived from length and time (speed =
dist/time) - km/hr, m/s
• concentration – derived from amount of substance
and volume(molarity = moles/vol) - mol/L
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metric prefixes
giga-
G
1,000,000,000
mega-
M
1,000,000
kilo -
k
1000
hecto-
h
100
deka-
dk
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base unit
meter, gram, mole,…
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deci-
d
1/10 or 0.1
centi-
c
1/100 or 0.01
milli-
m
1/1000 or 0.001
micro-
µ
1/1,000,000 or 0.000001
nano-
n
1/1,000,000,000 or
0.000000001
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1.4 Uncertainty in Measurement
• all measurements have some degree of
uncertainty
• smaller units always exists
• measuring tools have finite units of
measure
• anything after that finite unit is uncertain
• guess/estimate
• example – measure the width of your desk
with a meter stick
• graduated to nearest millimeter
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1.5 significant figures(i.e. sig figs, SF)
• significant figures/sig figs – a systematic method
of limiting the uncertainty(error) in measurements
and calculations
• sig figs – all numbers that have been measured
exactly + 1 digit as an estimate/uncertain
• example – width of desktop is exact to the nearest
millimeter + estimate (but only 1 digit)
• 475 mm = exact measure, but what about the little extra
that can’t be measured?
• 475.2 mm = measure in correct sig figs
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Rules for Counting Significant Figures Overview
1. Nonzero integers
2. Zeros
 leading zeros
 captive zeros
 trailing zeros
3. Exact numbers
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Rules for Counting Significant
Figures - Details
Nonzero digits always count as
significant figures.
3456 has
4 sig figs.
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Rules for Counting Significant
Figures - Details
Zeros
Leading zeros do not count as
significant figures.
0.0486 has
3 sig figs.
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Rules for Counting Significant
Figures - Details
Zeros
Captive zeros always count as
significant figures.
16.07 has
4 sig figs.
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Rules for Counting Significant
Figures - Details
Zeros
Trailing zeros are significant
only
if the number contains a
decimal point.
9.300 has
4 sig figs.
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Rules for Counting Significant
Figures - Details
Exact numbers have an infinite number
of significant figures.
1 inch = 2.54 cm, exactly
60 seconds = 1 minute,
exactly
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Rules for Significant Figures
in Mathematical Operations
Multiplication and Division: # sig
figs in the result equals the number
in the least precise measurement
used in the calculation.
6.38  2.0 =
12.76  13 (2 sig figs)
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Rules for Significant Figures
in Mathematical Operations
Addition and Subtraction: # sig figs in
the result equals the number of decimal
places in the least precise measurement.
6.8 + 15.6896 =
22.4896  22.5 (3 sig figs)
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Precision and Accuracy
• Accuracy – proximity of a
measurement to the correct/accepted
value.
• % error = (measured value – accepted value)
accepted value
• Precision – proximity of measures to
one another.
• no accepted value exists
• % deviation(lab report write-up)
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1.6 Dimensional Analysis
• problem solving technique that
uses units/labels and fractions
• driven by the unit/label of your
answer
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1.7 Temperature
• temp – measure of average kinetic
NRG of a system
• more KE = more temp
• SI unit = Kelvin/absolute scale
• 0 K = lowest possible temp
• uses same graduations as Celsius scale
• differ by 273
• 0 K = -273o C
• 273 K = 0o C
• 373 K = 100o C
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Temperature
• Celsius scale
• 0o C = freezing pt of water
• 100o C = boiling pt of water
• Fahrenheit Scale
• 0o F = freezing pt of salt brine(similar to ocean
water)
• 96o F = body temp(wrong temp, easy to divide)
• 32o F = freezing pt pure water
• 212o F = boiling pt pure water(180o , easy to
divide)
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Temperature
• conversions
• o C = K -273
• K = o C + 273
•
•
o
o
C = ((o F + 40) x 5/9) – 40
F = ((o C + 40) x 9/5) - 40
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1.8 Density
•Density - the mass of substance per unit
volume.
• how much stuff compared to how much space it takes up
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1.9 Classification of Matter
• matter – anything that takes up
space and has mass
• possess inertia
• Three States of Matter:
• Solid: rigid - fixed volume and shape
• Liquid: definite volume but assumes the
shape of its container
• Gas: no fixed volume or shape - assumes
the shape of its container
• Plasma: high NRG phase
• Bose-Einstein Condensate: low NRG
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phase
Composition of Matter
MATTER
Homogeneous
Heterogeneous
-same thru-out
-different thru-out
Solution
Pure substance
-one type of matter
only
- oxygen, water
Compound
-one phase, 2 or more
substances
-air, pop, stainless
steel
-2 or more subst.
Element
-simplest
-one type of atom
-lead, oxygen
Mixture
-2 or more subst.
-chem Rx to separate
-easily separated thru
physical means
-specific formula
-no formula
- different properties
- retain same properties
-water, carbon dioxide,
sulfuric acid
-may consist of diff. phases
Separation techniques
- distillation
- filtration
- chromatography
-
gas, paper, liquid(HPLC), thin
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physical property
- properties that can be observed/measured without
changing the substance
-density
-luster/color
-melting/boiling point
chemical property
- properties that describe how a substance reacts with
other substances in a chemical change
-highly reactive
-combines with oxygen
-burns in air
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physical change – change in appearance or phase of
matter
-no change in composition
-same substance, looks different
-dissolving sugar in water
-melting ice
chemical change – change in the identity or composition of
the substance
-chemical Rx needs to occur
-burning paper
-baking soda and vinegar(volcano Rx)
-reactant (s)– starting substance(s) = paper, baking
soda, vinegar
-product(s)- substance(s) created = carbon dioxide,
water vapor
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evidence of a chemical Rx
1. change in NRG(absorbed or released)
-substance gets hotter or colder
2. evolution of a gas
-bubbling
-change in odor
3. formation of light
-burning match
-glow stick
4. formation of electricity
-batteries/dry cells
5. formation of a precipitate
-precipitate = insoluble solid that falls out of solution
-soap scum
-hard water deposits/crust around faucet
6. color change
-chemical indicators – litmus
-not always reliable
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