Download 1-Fundamentals-ques 2007

Scientific & Chemical
Fundamentals
Dr. Ron Rusay
Fall 2007
© Copyright 2003-2007 R.J. Rusay
Scientific & Chemical
Fundamentals
1
Chemistry & the Scientific Method
 Matter : Classification & Properties
 Mathematics / Arithmetic:

Exponents, Significant Figures
Measurement & Units: (SI & metric)
 Conversions and Relationships:
Dimensional Analysis: Density, Percent
 VOCABULARY: Key Terms, Bold Style Learning

© Copyright 1998-2007 R.J. Rusay
Textbook Reading
Chemical Foundations
1.1 Chemistry: An Overview
1.2 The Scientific Method
1.3 Units of Measurement
1.4 Uncertainty in Measurement
1.5 Significant Figures and Calculations
1.6 Dimensional Analysis
1.7 Temperature
1.8 Density
1.9 Classification of Matter
Science & The
Scientific Method
QUESTION
The difference between a scientific law and a scientific theory can,
at times, be confusing. For example, we will refer to the “Atomic
theory” or perhaps the “Law of Gravity.” Should the Law of
Gravity be changed to the Theory of Gravity?
1. Yes, no one can see gravity, it is better described as a theory.
2. No, scientific laws are based on summaries of many
observations and gravity observations are well known and
predictable.
3. Yes, gravity is better described as a theory because gravity
explains why masses attract each other and theories are about
explaining observations.
4. No, keep it as a law, laws offer explanations and gravity
explains why masses attract each other and laws are about
explaining observations.
Some Possible Steps in the
Scientific Method
 1.
•
•
 2.
Observations
qualitative
quantitative
Formulating hypotheses
•
possible explanation(s) for the
observation
 3.
•
•
Performing experiments
 4.
Developing a theory
Testing & Refining
 5.
gathering new information
testing whether the hypotheses are valid
Chemistry: The Study of Matter
 In
all of its forms & all of its behaviors
 Sub-categories (not so distinct any longer)
•
•
•
•
•
•
•
•
Organic: carbon
Inorganic: non-carbon
Organometallic: organic + inorganic
Analytical: what?, how much?, how pure?
Biological / Biochemistry: living organisms
Physical: energy, changes, rates
Nuclear: the nucleus
Environmental: interdisciplinary, eg.
Oceanography
© Copyright 1998-2007 R.J. Rusay
Chemistry & Matter (Chemicals)
 How
many different chemicals do you
think have been reported in the
scientific literature?
A) 100,000
B) 1,000,000
C) 10,000,000
D) 100,000,000
E) 1,000,000,000
Chemistry & Matter:
Properties & States
1
• Physical vs. Chemical Properties
• Solid (s), Liquid (l), Gas (g)
• Homogeneous vs. Heterogeneous Mixtures
• Organization of atoms/molecules:
atoms/elements  molecules/compounds
• Extensive vs. Intensive Properties
Varies with amount (extensive) or does not vary
with amount (intensive)
© Copyright 1998-2007 R.J. Rusay
01_15
Matter
Organization of Matter
Heterogeneous
mixtures
Physical
methods
Homogeneous
mixtures (solutions)
Physical
methods
Pure substances
Classification
of Matter
Compounds
Chemical
methods
Elements
Atoms
Nucleus
Electrons
Protons
Neutrons
Quarks
Quarks
up,down, strange, charm, bottom, top
leptons
muons, tau,
neutrinos
The effects of a
magnet on iron: filings
in a mixture and atoms
in a molecule.
Types of Mixtures

Mixtures have variable composition of two
or more components.

A homogeneous mixture is a solution (for
example, vinegar: water + acetic acid, or steel
& bronze: solid metals)

A heterogeneous mixture is, to the naked
eye, clearly not uniform (for example, a bottle
of ranch dressing with two layers: water + oil,
or two solids: iron and sulfur)
Elements & Compounds
Element: A substance that cannot
be broken into simpler substances
by chemical means, eg. Fe, Iron or
S8 Sulfur
Compound: A substance with a
constant composition that can be
broken down into elements only by
chemical processes,eg. FeS, Iron
(II) sulfide
QUESTION
Is a cup of coffee a homogeneous solution or a compound? Which
of the following agrees with your reasoning?
1. The coffee in the cup is a homogeneous solution because it
contains the same components throughout, but there are many
compounds dissolved to make coffee.
2. The coffee in the cup is a compound because it has a set
ratio of components that make it the same throughout.
3. The coffee in the cup is both a compound and a solution.
It looks the same throughout like a true solution, yet it always
has the same amount of each component.
4. The coffee in the cup is a heterogeneous solution not
homogeneous because it contains distinct, different
compounds dissolved to make coffee.
Measurement & Units
(SI units & common units in General Chemistry)
1
• Quantitative vs. Qualitative
• MASS (Chem: gram; SI: kg)
• LENGTH (Chem: cm & others; SI: m)
• TEMPERATURE (Celsius & Kelvin; SI: K)
• VOLUME (Chem: mL; SI: Liter)
• CHEMICAL AMOUNT: Mole (mol)
© Copyright 1998-2007 R.J. Rusay
Units of Measure
Units
U.S.
SI
Chemistry
Mass (weight)
Pound (lb)
Kilogram (kg)
Volume
Gallon (gal)
u
Liter (L)
Temperature
Fahrenheit
(oF)
Mile (mi),
Feet(ft), Inches
(in)
Kelvin (K)
“ Gram”
(g, mg)
“ Liter”
(mL, L)
K & Celsius (oC)
Length
Time
Meter (m)
“ Meter”
(cm, mm, nm)
Second (s)
Second (s)
Mole (mol)
Mass and Volume
Measurement
Mass Determination
(Weighing Devices: Balances)
Volumes of regular shapes
V=s3
h
V=lxwxh
01_05
1m3
Volume
1dm3= 1 L
1cm3= 1 mL
1 cm
1 cm
Liquid Measurement Tools
Numbers & Measurement
The Importance of Units

Measurement - quantitative observation
consisting of 2 parts
• Part 1 - number
• Part 2 - unit

Examples:
• 20 grams
• 6.63   joules / second
Scale: Size & Comparison
 Macroscopic
vs. Microscopic
 IBM financed Video:
http://www.wordwizz.com/imagendx.htm
How would you compare your lifespan?.. to that
of a dog? ….to the age of the earth?…How
about the age of mankind to that of all life?..
..the age of industrialized mankind to the age
of mankind?
Graphic Comparisons
Powers of Ten:
Scale
Language describes scale (prefixes)
Shorthand Prefixes
How many zeroes does yotta yotta yotta have?
Commonly used prefixes in
Chemistry
These should be known from memory.
Commonly used prefixes in Chemistry
The dark ones should be known from memory.
QUESTION
Conveniently, a U.S. nickel has a mass of approximately 5 grams.
If you had one dollar’s worth of nickels what would be the mass
of the nickels in milligrams?
1.
2.
3.
4.
100 milligrams
50 milligrams
1,000 milligrams
100,000 milligrams
1000 milligrams (mg) = 1 gram (g)
Scientific Notation &
Significant Digits
Scientific Notation: A single digit followed by a
decimal and a power of ten.
Examples: 2,345 mL and 0.002340 g
2,345 mL = 2.345 x 10 3mL 0.002340 g = 2.340 x 10 -3 g
Numbers
1
• Expressing a number correctly is determined
by the method used in the measurement!
• How many numbers should I include?
Significant Digits (Figures)
Consider: the exactness of the measured value
• Short Hand expression translates the
number: Scientific Notation
© Copyright 1998-2007 R.J. Rusay
What is the length of the rod?
Different measurement tools give different numbers:
Which ruler is better?
? cm
4.2 - 4.3cm
? cm
4.24 - 4.25cm
Buret
08
mL
0
10
22.2 mL
20
30
40
50
What does each line represent?
1 mL
What can be estimated?
O.1 mL
Measurement Assignment
http://chemconnections.llnl.gov/General/Chem120/volume1.htm
Temperature Scales
Relative to Water
QUESTION
Dr. R. walks into class and claims, “It is very cold in here today. It
feels like 242 K.” If that were the temperature, would you agree
that you would feel cold? What would that be in Celsius degrees?
1.
2.
3.
4.
I agree, that would be 31°C.
I agree, that would be – 31°C.
I do not agree, that would be 31°C.
I agree, that would be –31.15°C.
Temperature
Precision & Accuracy
(a)
(b)
(c)
QUESTIONS:
1) Rank the images from best to worst precision.
2) Rank the images from best to worst accuracy.
QUESTION
Two Chem 120 students are each drinking a soft drink after class.
The volumes of both containers are respectively listed as 375
milliliters. Philip remarks that the law requires bottlers to be very
precise. Susan correctly responded:
1. If precision were the only requirement, bottlers could claim
any volume as long as it was always very nearly the
same volume.
2. Since precision is a requirement, bottlers have to get exactly
375 mL in every can.
3. Bottlers must have a precise average of all of the containers in a
case of soft drinks equal to 375 mL.
4. If there were a difference of no more than +/- 1 mL between
containers, the bottlers can sell their beverage.
Precision & Accuracy
Numerical Data
a)
b)
a)
9.5 2 9.52
8.3 6 8.36
7.2 9 7.29
8.3 4 8.34
_____
____ ____
___ ____
8.378
Averag eAvera ge
Roun d Off
Avera ge
Roun d Off
7.9 5 7.95
8.0 0 8.00
8.0 5 8.05
7.9 5 7.95
_____
____ ____
___ ____
7.988
8.38
7.99
9.52
8.36
7.29
8.34
__ ____ ____
8.378
b)
de vi atio n
-1.14
0.02
1.09
0.04
0.573
8.38 +/- 0.57
c)
8.4 0 8.40
8.3 5 8.35
8.4 2 8.42
8.3 6 8.36
_____
____ ____
___ ____
8.383
8.38
a)
c)
b)
8.40
8.35
8.42
8.36
__ ____ ____
8.383
c)
de vi atio n
-0.02
0.03
-0.04
0.02
0.028
8.38 +/- 0.0 3
Abs olute va lue ( all of the - becom e +)
de vi atio n
7.95
8.00
8.05
7.95
__ ____ ____
7.988
7.99
0.0 4
-0.0 1
-0.0 6
0.0 4
0.038
+/- 0.04
QUESTION
Rank the relative precision of the three sets of data:
a), b) and c).The accepted value is 8.08.
Average
Average
Average
a)
b)
c)
8.38
8.38
7.99
average
average
average
deviation
deviation
deviation
a)
b)
c)
+/- 0.57
+/- 0.03
+/- 0.04
A) Precision: a > c > b
B) Precision: b > c > a
C) Precision: a = b > c
D) Precision: a > b > c
QUESTION
Rank the relative accuracy of the three sets of data:
a), b) and c).The accepted value is 8.08.
Average
Average
Average
a)
b)
c)
8.38
8.38
7.99
average
average
average
deviation
deviation
deviation
a)
b)
c)
+/- 0.57
+/- 0.03
+/- 0.04
A) Accuracy: a > c > b
B) Accuracy: b > c > a
C) Accuracy: c > a = b
D) Accuracy: a = b > c
Reporting Numbers
Rules for Significant Digits (Figures)

Nonzero integers always count
as significant figures.
 3456
g has how many sig figs?
 4 sig figs.
• Expressed in scientific notation?
3.456 x 10 3 g
Reporting Numbers
Rules for Significant (Digits) Figures

Exact numbers (unit, conversion
or scale factors) can have an infinite
number of significant figures.
1
liter = 1,000. ml, exactly
1
inch = 2.54 cm, exactly
Systematic Problem Solving
Dimensional/Unit Analysis
How many mL of milk are in a1/2 gallon carton?
0.50 gal
1 gal = 4 qt
? mL
1 qt = 946 mL
0.50 gal | 1 qt | 946 mL = ? mL
| 4 gal | 1 qt
Complete the following
Units & Conversions
Number
13,000,000,000 yrs.
Scientific Notation
________________
___________ mL
______________ mL
____________ kg __8.45 x 10 -1 kg___
Named unit
__? gigayears
0.546 Liters
_? grams__
Zeros

Leading zeros do not count as
significant figures.

0.0486 mL has how many sig figs?
 3 sig figs.
• Number expressed in scientific
notation?
4.86 x 10 -2 mL
Zeros



Captive zeros always count as
significant figures.
16.07 cm has how many sig figs?
 4 sig figs.
Number expressed in scientific
1.607 x 10 1 cm
notation?
Zeros


Trailing zeros are significant only if
the number contains a decimal
point.
9.300 kg has how many sig figs?
 4 sig figs.
• Number expressed in scientific
9.300 kg
notation?
QUESTION
Which one of the following does NOT represent a result with four
significant digits?
1.
2.
3.
4.
0.07100
0.7100
0.7010
0.0710
Mathematics & Arithmetic
1
• Relative to method(s) of measurement
• Short Hand expression: Scientific Notation
• Numbers : How many to include?
Quantitative vs. Qualitative
• Addition/Subtraction......
• Multiplication/Division.....
• What is “significant”?.....Rounding Off
• http:dbhs.wvusd.k12.ca.us/SigFigsFable.html
© Copyright 1998-2007 R.J. Rusay
Computational Rules
1
• Addition/Subtraction: Answer expressed
•
to the least number of decimal places of
the figures in the process
Multiplication/Division: Answer
expressed to the least number of
significant figures
© Copyright 1998-2007 R.J. Rusay
Addition
 Four
students were each asked to
measure a piece of wire and provide a
total length for the four pieces.
 Report the result correctly:
0.05
12.01
1.9
+
2.386
_______
cm
cm
cm
cm
QUESTION
If you were unloading a 23.50 kg box of books from your car and
a “friend” added two more 482 gram chemistry books, how much
in kg and using the rules for significant digits, would you be
lifting?
1.
2.
3.
4.
23.98 kg
24.464 kg
24.46 kg
24.5 kg
Mathematical Processes:

Provide correct answers assuming each value (unit
omitted) is written with the correct number of sig figs:
12.01
x
1.90
_______ ______________
=
2.386
12.01
x
1.90
_______ ______________
+ 0.05 =
2.386
QUESTION
The average mass of a certain brand of vitamin C tablets is 253 mg.
What is the mass of three such tablets rounded to the proper
number of significant digits?
1.
2.
3.
4.
0.760 grams
0.759 grams
0.7590 grams
0.253 grams
Conversion Factor Method
(Dimensional Analysis)
1
• Qualitative Descriptions vs. Quantitative
• Use exact numbers / “scale factor” UNITS
• A Bookkeeping Method: Example
___ ft___in --------> ? m
• (1 ft = 12 in; 2.54 cm = 1 in; 100 cm = 1 m)
• ___ft x 12 in/ft + ___in = ___in
• ___in x 2.54 cm/in x 1 m/100cm = ___m
© Copyright 1998-2007 R.J. Rusay
Density
http://www.density.com/what.htm
• Density = Mass / Volume [g/mL or g/cm ; g/L]
• Least dense man-made solid substance:
3
1
Aerogel, D = 3.025 x 10-3 g/cm3
http://eetd.lbl.gov/ECS/aerogels/aerogels.htm
http://stardust.jpl.nasa.gov/spacecraft/aerogel.html
• D = 1.22 x 10 g/cm (1.22 g/L)
• Densest known substance: a White Dwarf
-3
air
3
http://antwrp.gsfc.nasa.gov/apod/ap961203.html
1.0 teaspoon = 3.0 T; D = ? g/cm3
(1 tsp = 4.93 mL; 1 mL = 1 cm3 )
© Copyright 1998-2007 R.J. Rusay
QUESTION
The volume of a sample can be obtained from its density and mass.
If the mass of a sample of acid from a battery were 5.00 grams and
the density was 1.2 g/mL, what would you report in mL and with
the proper number of significant digits, as the sample volume?
1.
2.
3.
4.
6.0 mL
6.00 mL
4.2 mL
4.17 mL
QUESTION
Which would provide more grams of NaCl, sample one with a
mass of 2,350 mg, or sample two, a solid with a volume of 2.00
cm3? (The density of solid salt is 2.16 g/cm3.) Report your choice
and report the grams of the more massive sample.
1.
2.
3.
4.
Sample two; 1.08 grams
Sample two; 4.32 grams
Sample one; 2.35 grams
Sample one; 2.350 grams
Percent
1
• A comparison based on normalization to
100.
• George Washington University: 64
unsealed addressed envelopes with $10 in
each were dropped on campus in different
classrooms.
• In economics 18 of 32 were mailed, in
business, history and psychology 10 of 32
were mailed. What is the percent for each
of the 2 groups of students?
© Copyright 1998-2007 R.J. Rusay
Percent Continued
1
• The Professor conducting the study
received 43.75% of the $640 in the
mail. How much did he receive?
• How many of you would mail the
envelop presuming no one knows you
found it?
• One student mailed an empty envelop
with the return address: Mr. IOU, 1013
Indebted Lane, Bankrupt City, MS (WSJ
© Copyright 1998-2007 R.J. Rusay
1/18/95)