Chemistry is called “The Central
Science” because it overlaps so many sciences.
Why Should YOU Study
Chemistry?
•   Chemistry is everywhere and in everything
–   Chemistry gives you a better understanding of the world.
•   “There is a sucker born every minute” –
PT Barnum
•   You don’t want to be that person
•   Chemistry is fun. No, really!
–   Pop rocks, fireworks, lava lamps, everything you eat, how things cook, and many toys are based on chemical principals that we’ll cover this year
1

What is the Chemistry?
What are the sub-fields in Chemistry?
How does it fit into
“science” as a whole?
Classification of the sciences
•   One way to classify the sciences is to divide them into three basic types:
–   Physical sciences
–   Life sciences
–   Social sciences
2

Classification of the sciences
•   Physical sciences attempt to explain natural non-living objects and phenomena
–   Chemistry, physics, geology, and astronomy
•   Life sciences deal with living things
–   Biology and medicine
•   Social sciences deal with human behavior and civilization
–   Economics, anthropology, sociology, psychiatry, even education
Chemistry
•   Anywhere
–   on Earth or in stars
•   Any change
–   Physical, chemical, or nuclear
3

Six Major Divisions of
Chemistry
•   Organic Chemistry
–   Carbon-based chemistry
•   Fuels, plastics, synthetic fabrics, varnishes and coatings
•   Applies to biochemistry and environmental chemistry
•   Biochemistry Chemistry
–   The Chemistry of Life
•   Animal and plant sciences; genetics, medicine
•   http://cas.bellarmine.edu/chemistry/chemdept/faculty/Sinski/Pre-Med/chem1.doc
Six Major Divisions of
Chemistry, cont’d
•   Physical Chemistry
–   Related to the physical principles behind chemical behavior
•   Heat, work, energy, atomic structure and behavior
•   Inorganic Chemistry
–   The chemistry of all elements other than carbon
•   Mining, metal work (steel, titanium, aluminum, alloys), semiconductors and silicon- based chips
•   http://cas.bellarmine.edu/chemistry/chemdept/faculty/Sinski/Pre-Med/chem1.doc
4

Six Major Divisions of
Chemistry, cont’d
•   Analytical Chemistry
–   The science behind determining the amounts of materials in samples
•   Water testing, drug tests, quality assurance, manufacturing facilities
•   Environmental Chemistry
–   Apply chemical principles to the study of the environment
•   Soil testing, determining the amounts and effects of pesticides, monitor pollution
•   http://cas.bellarmine.edu/chemistry/chemdept/faculty/Sinski/Pre-Med/chem1.doc
But can also include subsets:
•   Nuclear (Physical)
•   Polymer (Organic)
•   Materials (Inorganic, but can also be organic)
•   Thermochemistry (Physical)
•   Pharmaceutical (Biochemistry)
•   Medicinal (Biochemistry)
•   Geochemistry (Environmental, Organic,
Inorganic combo)
•   Astrochemistry (Physical)
•   Crystallography (Physical, Analytical)
•   Nanotechnology (Organic, Physical, Analytical)
•   Forensics (Analytical, Organic, Inorganic,
Biochemistry, Physical)
•   http://cas.bellarmine.edu/chemistry/chemdept/faculty/Sinski/Pre-Med/chem1.doc
5

Chemistry the Science
•   What all of the sciences have in common is that they use scientific methods.
•   What is are scientific methods?
Are they the same as the scientific method we have learned since grade school?
•   What all, exactly, are we talking about here?
How Do We Gain Knowledge?
•   How do humans learn new things?
•   Two basic methods:
–   Revelation
–   Experimentation
6

Revelation
•   Somebody gives us the information
(it is revealed to us).
•   Believe or disbelieve information
•   based on our opinion of the validity of the source.
•   Very common.
•   Examples:
•   College Lecture Course
•   A Religion’s “Sacred Text”
Experimentation
•   We gather the information ourselves.
•   Believe or disbelieve
•   based on our opinion of the validity of the data.
•   Examples:
•   Scientific methods
•   Comparison Shopping
7

Examples
•   Let’s consider a hypothetical situation:
You are young. You are exploring your house and you have become interested in the burners on the stove. You want to know how they feel.
The first way to answer the question
•   Mom or Dad notices you near the stove; they give you a warning …
•   “Careful! Hot!”
–   Revelation: warning from parent.
–   Information gained: the object is hot. Touching it will hurt.
–   Possible conclusions:
•   Mom/Dad is wrong (invalid source); go ahead and touch.
•   Mom/Dad is right; don’t touch.
8

The second way:
Experimentation
•   No parent is near by, so you reach out and touch the burner yourself.
•   “$#@!%”
–   Experimentation: You touch the hot object yourself.
–   Information gained: Object is hot.
Touching it hurt.
–   Conclusions:
•   Data are valid – object is hot.
•   Don’t touch again!
The Basic Idea…
•   When you find out something by learning it from someone else, that’s revelation .
•   When you find out something by figuring it out for yourself, that’s experimentation , or using
Scientific Methods
9

Burner alternative:
•   Maybe the burner was not on and it was not hot at that time, and you now think it is fine.
•   However, it is possible that at some point in the future, you get burned when you touch it.
•   The point is, you can modify your beliefs after learning something new, and specifically after experimentation.
•   That’s what all the arrows are about.
•   Scientists retest and modify all the time
•   It’s their job
•   How they do it … .
steps there are in the scientific method that you have been taught
10

One possible set
11

12

Ummmmm….
•   There is no one “Scientific Method” that is a required list of steps all scientists follow sequentially.
•   In fact, many scientists go back and forth between steps many times
•   It’s why there are so many arrows
•   However, there are patterns to the behavior of scientists that are what we can collectively call “Scientific Methods”.
“Scientific Methods”
•   Generally agreed upon are:
1.
Observation
2.
Formation of a hypothesis
3.
Data collection via an experiment
4.
Forming conclusions
•   All other pieces usually fit in to one of those four categories
13

Revision, revision, revision….
•   Jumping between steps happens
•   However, you can’t have a conclusion before you experiment
•   You can, however, do things like modify your hypothesis midexperiment
•   Make new questions
•   Make changes to the experiment to answer new questions the next time around
A Good Summary:
14

Observation
Facts about what you:
•   See
•   Smell
•   Hear
•   Taste
•   Feel
Without adding any thoughts on the matter (like “it smells fabulous”; that would be an opinion, not a fact
Ex: Cooking bacon
Observations are made
Without adding any thoughts on the matter, such as
•   “it smells fabulous … .”,
Or
•   “Baconaise?! For real- for real?!
That is awesome!”
Or
•   “Kevin Bacon is old.”
Or
•   “That old dead guy should not be wearing that hat.”
•   These things are all opinions.
–   Yes- opinions ARE important in science. But not during observation.
15

Observation
Facts about what you:
•   See: color change from red to brown
•   Smell: like bacon
•   Hear: like sizzling
•   Taste: like bacon
•   Feel: like it goes from slimy to crispy
Hypothesis
•   A statement that explains the observation
–   Most are phrased as “If … .then
… ” statements, but they do not need to be
•   If I cook the bacon a shorter amount of time, then it will not taste burnt
–   Alternative, not as an “If … then … ” :
Reducing cooking time will result in better bacon
16

Control Experiment
•   Make several batches of bacon, cooking each batch a different amount of time
•   Relates back to the hypothesis
–   This is not a coincidence
–   The experiment must test the hypothesis
Controls and Variables
•   Controls stay the same
–   The pan/ griddle
–   The heat setting
–   Type / brand of bacon
•   Variables change
–   only one should be controlled for at a time
•   here, the cooking time
17

Independent Variables
•   What you set/ measure in the experiment
–   It is the cause of the change
–   In this case, it is the cooking time
The Dependent Variable
•   Is the outcome/ response that is measured
•   Responds to the independent variable
•   Named so because it depends on the dependent variable
–   It is the consequence of the independent variable
–   In this case, the degree of doneness of the bacon
18

Side note on experimentation
•   Not all experiments are performed as control experiments with a independent variable assigned at certain intervals
•   Experiments can also be observational
–   Ex: following the health of two cohorts
(smokers and non-smokers) for 20 years to determine the impact of smoking on lung health.
–   What would be the dependent variable here?
•   _______________________
What are the benefits of this type of study?
The drawbacks?
Do you think that they are often used in Chemistry?
If so, which field?
19

After the experiment:
Reporting
•   How scientists report data is not a step of the scientific method, although many scientists do report their findings in professional journals.
Formal reports typically include:
•   Title
•   Abstract
•   Introduction
–   Background
–   Purpose
•   Results
–   Data
–   Observations on the experiment
–   Results
•   calculations
–   Hypothesis
•   Discussion
•   Experimental
Methods
–   Materials
–   Procedure
–   Error analysis
–   Conclusion
See your CRH for more details on each; there is a lot of information there!
20

Data vs. Results
•   Data
–   Is usually listed in a table or a chart
–   Does not include calculations
–   Is not an explanation of what happened
•   Results:
–   Include calculations of raw data
–   Graphs that show relationships between data
•   line graphs
–   Explain the data
Using Data Tables in
Science
•   Data tables display data in an easy to read format
•   You can quickly locate and see desired information, rather than read it, which is usually included in brief
21

Data Table of Bacon vs.
Cooking Time
Number of pieces of Bacon Cooked in Batch
20
Number of pieces of Bacon Burned
0
Cooking Time
(minutes)
0
20
20
20
20
20
20
20
20
20
20
18
20
20
20
20
20
0
1
0
0
10
12
14
16
18
20
6
8
2
4
Results
•   Results are written up, often with the aid of graphs
•   Will include any calculations made, and the formulas used to make them
•   Tell if results make sense
–   are the mistakes insignificant enough to give credibility to the data?
•   Usually include
–   Percent yield
–   Percent error
22

Results
•   Percent yield
–   How much you got from the expected amount
% Yield = mass of Actual Yield x ( 100%)
mass of Theoretical Yield
•   Percent error
–   How close your answer is to the actual answer
% Error =
׀
Experimental value- Theoretical value
׀
x ( 100%)
Theoretical value
Graphing in science:
How we display data
1.
Always title your graph
–   Make sure it is about what you are graphing
•   Always Independent variable Vs.
Dependent variable
2.
The x-axis is always the independent variable; the y-axis the dependent variable
3.
Label the x and y axes, and use units with these labels
23

Graphing in science:
How we display data
4.
Use a line graph (scatter plot)
–   when you are trying to show how two things relate to each other
•   such as the dependent and independent variable
–   unless you are comparing numbers of things
•   which is NOT about comparing dependent and independent variables
–   Then use a pie chart or a bar graph
•   A good rule of thumb is that units imply a line graph, counting or percentage implies another type of graph
Graphing in science:
How we display data
5.
Use a best fit line for the line graph/ scatter plot
–   Do not just connect all the dots
6.
Use the space you are given
–   If you have a full page, take up the page
•   Using only a 10cm by 10cm square when you have a full page makes it much harder to read and get your point across
24

The Effect of Cooking Time on Bacon
20
18
16
14
12
10
8
6
4
2
0
0 5 10 15 20 25
Independent Variable (you control) Cooking time (minutes)
•   In this case, you are observing how many more pieces of bacon are burned with a change in cooking time.
Evaluation: The Arrows
How do you know if your results are acceptable?
25

Evaluation
•   Did you test your hypothesis?
•   Were your sources of error significant? Where they acceptable?
•   Were your data/ results within acceptable ranges?
–   Accurate? Precise? Or are you making claims you can not justify?
•   Can this go any further? Be modified to learn more?
•   Reflections?
After we know something
Assuming we are happy with the results, what happens when we are pretty darn sure we know something, and scientists recognize it as truth?
26

When experiments lead to knowledge: Laws and
Theories
•   If it all makes sense, and is supported, science incorporates that new knowledge into scientific knowledge as a whole in the form of a law or a theory
Laws
•   Statement of what happens without explaining why
•   It is a generalized relationship
•   Usually covers a small set of patterns/ behaviors
•   We can not not do it
–   Unbreakable so far
•   Usually has mathematical support
27

Theory
•   A hypothesis, or series of hypotheses, that have been tested extensively and have not been rejected
•   Covers a broad number of concepts/ behaviors/ observations
–   Explains why/ how things happen
–   Make predictions based up on
•   As close to truth as you can get
Relating laws and theories
•   Boyle’s law relates pressure and volume
–   Pressure and volume of a gas in a sealed container have a direct relationship; if one changes, the other changes in response
•   P
1
V
1
=P
2
V
2
•   The kinetic molecular theory explains Boyle’s law and can be used to predict gas behavior
–   Molecules moving exert pressure that pushes on the walls of a flexible container; as that pressure changes, the volume changes accordingly
28

But how do we know if we are right?
Evaluation of the
Experiment and Resulting
Data
Accuracy and Precision
A sidebar before we talk about using numbers in evaluation more … ..
29

Accuracy
Precision
–   How exact an answer is: to what place the answer is reported to
•   By use of significant digits (which we’ll get to shortly)
30

Accepted value/ target
Accuracy depends upon the definition of accurate for that particular situation
Ex: +/- 5% is OK for lab percent yield, but an unacceptable error for not hitting pedestrians while driving
Random Measurements
•   Measurements do not have precision --they do not cluster around the same value.
•   Measurements are probably not accurate the average does not represent the true value.
–   An accurate average does NOT make you accurate!
31

Are the following accurate? Precise? Neither?
32

33

Error: 2 types
•   Systemic error
–   Happens because of the instruments or methods used is consistently flawed
–   can be accounted for and adjusted for to get the “real” value
–   ex: the balance measures 0.05g heavy on every measurement
•   Corrected by adding 0.05g to all measurements
34

•   Random error
–   not a consistent part of the instruments or methods used
–   can not be accounted and adjusted for as it is not predictable
–   Examples
•   Not zeroing (tareing) the balance before a measurement
•   Contamination of a measuring device
Errors vs. Uncertainty in
Measurement
•   Errors in measurement are not the same as uncertainty
–   Humans mess up
–   Measuring instruments themselves are not 100% flawless
–   Both of these errors can be random or systemic
•   Error means it is done wrong, and uncertainty is not incorrect, just the limit of the measuring instrument
35

Uncertainty in
Measurement
•   ALL measurement involves some uncertainty, because all measurements involve some rounding.
•   Not an error, as long as you are rounding to the proper place
–   Defined by the markings on the instrument you are using
»   You are to go one decimal place
PAST the markings on the instrument
Measurements and
Estimation
•   You are told to draw a line
long using a regular ruler with marks for each millimeter
•   When you measure it out, you know that you are correct with the 35, but you had to estimate the .5 portion
–   You can be a little over or a little under
•   Up to 0.05cm (.5mm) up (to 35.55cm) or down
(to 35.45cm); you estimate one place past the smallest marks on the ruler
–   B/c both would round to 35.5cm
36

Rounding
•   Remember when rounding to a place
–   Look to the NEXT place ONLY (not past that)
–   Round down for 4 and below
–   Round up for 5 through 9
•   Examples:
•   223.459L rounded to the ones place is
223L
–   You look at 223.
4 59 and ignore the rest, 4 rounds down
•   223.459L rounded to the tenths place is
223.5L
–   You look at 223.4
5 9 and ignore the rest, 5 rounds up
Practice Rounding
Round the following to the hundreds place
§   34, 345
§   52, 299
§   2,303
Round to the hundredths place
§   234.4234
§   0.456645
§   63.54001
37

How to Measure
•   The last digit is always estimated
•   See
How to Read a
Graduated Cylinder
•   This is why we use significant digits in calculations
Measurements and
Estimation
•   The measurement has 3 digits to read
55.6mL
–   2 known: 55mL
–   1 estimated: 0.6mL
•   It can be a little off
–   To round to 55.6mL
(and not be 55.5mL or
55.7mL)
38

Measurements in the Lab:
Example A
30 mL
20 mL
10 mL
Downloaded from central.spps.org/uploads/ density abbreviated.
ppt
13 mL
Example B
0 mL
1 mL
2 mL
0.67 mL
n
Report what is known with certainty n
Add ONE digit of uncertainty
(estimation) n
By adding additional numbers to a measurement – you do not make it more precise. The instrument determines how precise it can make a measurement. Remember, you can only add ONE digit of uncertainty to a measurement.
Davis, Metcalfe, Williams, Castka, Modern Chemistry, 1999, page 46
39

1 2 3 4 5
4.5 cm
1 2 3 4 5 4.54 cm
1 2 3 4 5 3.0 cm
Timberlake, Chemistry 7 th Edition, page 7
n
Certain (known) numbers q
When you make a true count of something, it is exact n
The number of people in PHS n   n
The number of hours in the day
Can be a definition of a unit: q
Applies only to conversions within the same system (metric-metric or English-English)
§
12In = 1ft
§
1m= 100cm
40

Side note on two types of numbers: Certain n   and Uncertain
Uncertain numbers: Estimates q
Rounding a count q
1300 students in PHS, not the exact count q   q
Conversion factors that are not definitions
§
Metric- English/ English-Metric
§
§
1cm= 0.39370078740157477in
We’d usually round to something here as this is too long to use, as would be the answer from using this conversion n
Measurements
Include the certain digits and a last estimated digit
Using Significant Figures reflects precision by estimating the last digit n
What is the certain measurement? n
What is the estimated measurement?
Downloaded from central.spps.org/uploads/ density abbreviated.
ppt
41

The instrument determines the amount of precision of the data. n   n
What is the certain measurement here?
What is the estimated measurement here?
Downloaded from central.spps.org/uploads/ density abbreviated.
ppt
Some new, mostly review:
•   Significant Digits
•   Scientific Notation
•   System Internacional (SI)
•   Metric system
•   Unit Conversions
•   Dimensional analysis
42

Precision in Measurement
n
Tell us how good (precise) our measurement or calculation is q
Where the known digits and estimated digit are n
Are the digits that are important for calculations and ensure that you do not carry out an answer to the 23 rd decimal place when doing a calculation q
You don’t just pick the first three numbers, or 3 decimal places
43

Significant Figures in Measurements n   n
Significant digits include q   q
the known digits and the last (estimated) digit in a measurement.
8.45mL has three significant figures q   q
8 and 4, which are known
5 which is estimated n   n
You can’t read more than this on this graduated cylinder
Read one digit past the markings q
In this case, to the hundreds place
Working with Numbers: Significant Digits n
In a count of something, all digits are significant because we know that all numbers are exact n
How can you tell how many digits in a measurement are significant? q
All non-zero numbers are significant q
Zeros are what you need to think about
Zeros that are Significant
In the middle of a number.
Zeros that are Not Significant
•   When it’s a placeholder.
202 •   Before a number: 0.0035
•   At the end when there is
NOT a decimal point: 200
44

n   all zeros are significant in 202.00 q
Between non-zero numbers q
Or following a decimal point n   no zeros are significant in 0.0002 q
All are placeholders n   zeros MAY be significant in 2000 q
Depends on if it is a count or a measurement n   n
Yes if a count
No if a measurement because they would be placeholders
n
The following three measurements have very different degrees of precision, and therefore a different number of significant digits:
100g
100.g
100.0g
45

n
(Significant Figures)
100g rounded to the hundreds place q   the real value is between 51-149 q
1 significant digit n
100.g rounded to the ones place q   the real value is between 99.5-100.4 n   q
3 significant digits
100.0g rounded to the tenths place q   q   the real value is between 99.95-100.04
4 significant digits
The difference is the presence of a decimal
46

Give the number of significant figures in: n
1025 km n
2.00 mg n
0.00570 n
520
Rounding rules are the same as for measurements:
47

The Atlantic- Pacific Rule:
A trick to count significant digits
Pacific
Ocean
Point
Present count from this side
Start with first nonzero number
Atlantic
Ocean
Point
Absent count from this side
n   n
Line up the decimal points of the measurements to be added or subtracted
Perform the mathematical operation n   n
Round off the answer to the smallest number of decimal places in a measurement
For example: 2.50 + 2.5 = 5.0
48

n
The measurement containing the fewest significant figures determines the number of significant figures in the answer. n   n
Example 1: 2.8 m x 0.2 m = 0.56 = 0.6 m 2 n   since 0.2 only has 1 significant digit, and 2.8 has 2 significant digits, the answer must have only 1 significant digit
Example 2: 252 mi / 3.2 hr = 78.75 = 79 mi/hr n
Since 3.2 has 2 significant digits, and 252 has 3 significant digits, the answer must have 2 significant digits
S
N
Representing numbers large and small
49

U SING E XPONENTS (S CIENTIFIC
N OTATION )
1,000,000 = 10 6
10,000 = 10 4
1000
100
= 10 3
= 10 2
10
1
= 10 1
= 10 0
0.1
0.01
= 10 -1
= 10 -2
0.001
= 10 -3
0.0001
= 10 -4
0.00001 = 10 -5
0.000001 = 10 -6
S CIENTIFIC (E XPONENTIAL ) N OTATION
•   Conveniently expresses very large or very small numbers
•   245, 000, 000 is 2.45
X
10 8
•   2.45
E
8 is also acceptable
•   0.000 000 012 is 1.2
X
10 -8
•   1.2
E
-8 is also acceptable
•   Unambiguously expresses the number of significant figures
•   All the digits before the
X
10 (or the E) in scientific notation are significant
•   Remember the 100g, 100.g, and the 100.0g?
50

S
CIENTIFIC
N
OTATION AND
S
IGNIFICANT
D
IGITS
Number Number of
Sig Figs
100g
100.g
100.0g
1
3
4
Scientific
Notation
1
E
3g
1.
E
3g
1.00
E
3g
•   Scientific notation allows us to express this measurement with 2 significant digits while normal numbers do not.
•   1.0
E
3g would tell us that the balance rounded to the tens place
H OW TO C ONVERT A N UMBER TO
S CIENTIFIC N OTATION
1.
Convert the number you’re converting into a number between 1 and 10 by moving the decimal either to the left or to the right.
2.
Write the number that you came up with in step one, followed by “x 10”. (You can also use E in place of this)
3.
Recall how many decimal places you moved the decimal point in step one.
•   If the number that you’re converting is greater than 10, write a positive number as a superscript above the “x 10” from step 2.
•   If the number you’re converting is less than one, write a negative number.
51

P RACTICE P ROBLEMS : W RITE THESE
NUMBERS IN NORMAL FORMAT
¢
4.2 x 10 3
¢
2.50 x 10 6
¢
¢
¢
4.35 x 10 2
6.830 x 10 -2
7.32 x 10 -4
¢
4.890 x 10 3
¢
7.34 x 10 -5
¢
1.32 x 10 3
P
RACTICE
P
ROBLEMS
:
WRITE THESE
NUMBERS IN SCIENTIFIC NOTATION
¢
45,500
¢
0.000 234
¢
45, 500.
¢
0.0045
¢
250
¢
0.000250
¢
7,300
52

You  ARE  going  to  use  it
The  English  System  is  not  allowed  in  Science
SI Unit Metric
System
English System
Mass kilogram (kg) gram (g) lb
Length
Volume
Time
Temperature
Amount
Energy
Pressure meter (m) meter (m) yd cubic meter
(m 3 ) second (s) liter (L) second (s) qt
Kelvin (K) Celsius
(ºC)
Farenheit (ºF)
Mole (mol) Mole (mol) Mole (mol)
Joule (J) Joule (J) Calorie (cal)
Pascal (Pa) Pascal (Pa) Atmosphere
(atm)
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WHY WE CARE
Giga    G  1,000,000,000    10 9
Mega  M  1,000,000      10 6   kilo    k  1,000      10 3   deci    d  .1
10 -­‐1   cenG    c  .01        10 -­‐2   milli    m  .001        10 -­‐3
Micro  µ  .000001      10 -­‐6   nano    n  .000000001
10 -­‐9   pico    p  .000000000001    10 -­‐12
9/18/15 1.4
Metric  Conversion  ArGcles
•   Small  Group  Discussion  [A,  B,  C,  D]
–   What  happened  in  your  arGcle?
–   Why  did  it  happen?
–   How  could  this  be  avoided  in  the  future?
•   Large  Group  Discussion
–   How  are  all  of  the  arGcles  connected?
–   Should  the  U.S.  change  to  the  S.I.  (or  metric)   system?
–   What  problems  would  there  be  because  of  the   change?
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Because  it  is:
1.
Standard
–   the  whole  world  uses  it
–   Except  the  US,  Libya,   and  Myanmar  (Burma)
2.
Base  10
–   Easy  conversion   between  units
3.
Units  make  more  sense   than  English  units
Dimensional Analysis
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Dimensional Analysis and
Conversion Factors n   Dimensional analysis is a systematic approach for solving problems by multiplying a measurement by one or more conversion factors with units. n   Conversion factors are ratios or fractions derived from definitions or equalities n   3 ft = 1 yd n   16 oz = 1 lb.
Conversion Factors
•   Each equality can be written as two conversion factors
•   The equality below gives the two conversion factors on the right:
•   The correct one to use depends on which unit you want your answer in
–   The unit you want goes on the top
1 yd = 3 ft
⎛ 1 yd
⎝
⎜
3 ft
⎛
⎜
⎝
3 ft
1 yd
⎞
⎟
⎠
⎞
⎟
⎠
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Sample Problems
•   How many feet are there in 25 yards?
( 25 yd )
⎛ 3 ft
⎜
⎝ 1 yd
⎞
⎟ = ?
⎠
•   How many yards are there in 12 ft?
€
( 12 ft )
⎛ 1 yd
⎜
⎝
3 ft
⎞
⎟ =
⎠
?
Practice Problems
•   How many ounces are there in 3.5 lb?
( 3 .
5 lb )
⎛
⎜
⎝
16 oz
1 lb
⎞
⎟
⎠
= n
How many gallons are there in 12 quarts?
( 12 qt )
⎛
⎝
⎜⎜
1 gal
4 qt
⎠
⎟⎟
⎞
=
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Metric to Metric Conversions
•   Metric to metric conversion factors are derived from the definitions of metric prefixes.
•   These are exact numbers with unlimited Sig Figs
–   Because they are definitions
0.1 meter = 1 decimeter
1 meter = 10 decimeters
0.01 meter = 1 cm
1 meter = 100 cm
Sample Problems
•   How many decimeters are there in 5.5 meters?
( 5 .
5 m )
⎝
⎜
⎛
1 dm
1 x 10 −
1 m
⎠
⎟
⎞
= n
How many meters are there in 25 centimeters?
( 25 cm )
⎝
⎜⎜
⎛ 1 x 10 − 2
1 cm m
⎠
⎟⎟
⎞
=
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English to Metric Factors
•   English to Metric conversion factors are derived from tables of equivalent values, for example:
•   Remember that you need to keep in mind that these conversion factors are estimated, not exact, like conversions within the same system
Practice Problems
454 g = 1 lb 1 L = 1.06 qt 2.54 cm = 1 in
•   How many grams are there in 125 pounds?
( 125 lb )
⎛
⎜
⎝
454 g
1 lb
⎞
⎟
⎠
= n
How many inches are there in 8.7 meters?
( 8 .
7 m )
⎛
⎜
⎝
1 cm
1 x 10 − 2 m
⎞
⎟
⎠
⎛
⎜
⎝
1 in
2 .
54 cm
⎞
⎟
⎠
=
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Temperature
Scales
Freezing point of water:
32º F = 0º C = 273 K
Boiling point of water:
212º F = 100º C = 373 K http://library.tedankara.k12.tr/chemistry/vol2/pressure%20and%20temprature/z7.gif
Temperature Conversion
•   Fahrenheit degrees are smaller than Celsius
–   But the Fahrenheit scale is scientifically unimportant
•   100 º C is the equivalent of 212 º F
•   0 º C is equivalent to 273K
–   Based on 0K as the lowest temperature possible
ºF = 1.8* ºC + 32 º
ºC = (ºF - 32 º) / 1.8
K= ºC + 273
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Practice Problems
•   What is 75.0 º F in ºC?
•   ºC = (75 º F- 32 º ) / 1.8 = 23.8 ºC
–   But use a ºC thermometer and you’ll never need to convert
–   Take ALL temperatures in ºC
•   What is -12 º C in ºF?
•   Who cares? You’ll NEVER EVER go from ºC to ºF in this class, b/c ºF is irrelevant in science classes
•   It’s 10.4 ºF, for the record (1.8)(-12) +32=10 in case you
•   What is 100 ºC in K?
•   100º C + 273= 373K
•   Kelvin scale IS important to chemistry
•   Know K to ºC conversions and ºC to K conversions
K= ºC + 273 and ºC = K - 273
Density
§   Density is a measure of how tightly packed and how heavy the molecules are in an object.
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Density
•   Density = amount of matter per unit volume
•   Density  =        Mass
Volume
•   Mass usually expressed in grams
•   Volume usually expressed in cm 3 or mL.
•   So density’s units are g/cm 3 or g/mL
•   Density is the ratio of mass to volume
§   If the volume stays the same and the mass increases . . . the density will increase.
§   If the mass stays the same and the volume increases . . . the density will decrease.
The  “DMV”  Triangle  for
Volume,  Mass,  and  Density
Density =
M
V
Volume =
M
D
Mass = = x V
M
D X V
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OR
Density is the measure of the
“compactness” of a material
Compactness
1.
How close the atoms or molecules are to each other.
2.
More than “ heaviness ” … density includes how much space an object takes up!!
3.
All substances have density including liquids, solids, and gases.
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