Welcome to the World of Chemistry Mrs. Panzarella Rm. 351

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Welcome to the World of ChemistryMrs.
Panzarella Rm. 351
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Chemistry
The Central Science
Health and Medicine
Nuclear Chemistry
Astronomy
Biology
Physics
Biology
Geology
Environmental Science
Plant Sciences
Biochemistry
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Branches of Chemistry

• Many major areas of study for specialization
• Several career opportunities
• Also used in many other jobs

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1. Organic Chemistry

• Organic is the study of matter that contains
  carbon
• Organic chemists study the structure, function,
  synthesis, and identity of carbon compounds
• Useful in petroleum industry, pharmaceuticals,
  polymers

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2. Inorganic Chemistry

• Inorganic is the study of matter that does NOT
  contain carbon
• Inorganic chemists study the structure, function,
  synthesis, and identity of non-carbon compounds
• Polymers, Metallurgy

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3. Biochemistry

• Biochemistry is the study of chemistry in living
  things
• Cross between biology and chemistry
• Pharmaceuticals and genetics

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4. Physical Chemistry

• Physical chemistry is the physics of chemistry
  the forces of matter
• Much of p-chem is computational
• Develop theoretical ideas for new compounds

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5. Analytical Chemistry

• Analytical chemistry is the study of high
  precision measurement
• Find composition and identity of chemicals
• Forensics, quality control, medical tests

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The Language of Chemistry

• The elements, their names, and symbols are given
  on the PERIODIC TABLE (along with reference
  Table S)

Dmitri Mendeleev (1834 - 1907)
http//www.youtube.com/watch?v6b2Uy1TDAl4
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Chemical Symbols

• Each element on the periodic table is represented
  by a chemical symbol

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Chemical Symbols(continued)

• NOTICE!!
• The Chemical symbols with two letters are written
  with a capital first letter and lowercase second
  letter

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ELEMENTS TO KNOW

• Atomic numbers
• 1-38, 47, 50-56, 74, 78-80, 82-84, 86, 92, 94

• LEARN the name and chemical symbol
• spelling counts-use Table S or Agenda (pg R-7)
• Complete pages 2-3 in Learning Guide
• Quiz Thursday

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Chemistry

• The study of matter, energy and their interactions

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Measurement
1) N3 No Naked Numbers. All measurements and
answers to math problems must have units written
after the numbers. 2) No Work, No Credit. You
must show the math set-up when doing math
problems.
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Measurement

• Qualitative observation
• Focus on the qualities of an object.
• Ex. Color of an object
• Quantitative observation
• Characteristics of an object that can be
  measured.
• Ex. Mass, Length

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Accuracy vs. Precision

• Accuracy - how close a measurement is to the
  accepted value
• Precision - how close a series of measurements
  are to each other

ACCURATE CORRECT PRECISE CONSISTENT
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Can you hit the bull's-eye?
Three targets with three arrows each to shoot.
Both accurate and precise
Precise but not accurate
Neither accurate nor precise
How do they compare?
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Figure 1.16
Precision and accuracy in the laboratory.
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Significant Figures

• Indicate precision of a measurement.
• Includes all digits that can be known precisely
  plus a last digit that must be estimated

2.35 cm
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Figure 1.14
The number of significant figures in a
measurement depends upon the measuring device.
32.3 oC
32.33 oC
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Rules for Significant Figures

• a. All non-zero digits are significant

b. Zeroes between non-zero digits are significant
c. In measurements containing an expressed
decimal, zeros to the right of NON-ZERO digits
are significant.
http//www.youtube.com/watch?vZuVPkBb-z2I
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Atlantic/Pacific Rule
Pacific Decimal Present Atlantic Decimal
Absent
Count from the ocean towards the coast starting
with the first nonzero digit, and include all the
digits that follow
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Significant Figures
Counting Sig Fig Examples
1. 23.50
1. 23.50
4 sig figs
3 sig figs
2. 402
2. 402
3. 5,280
3. 5,280
3 sig figs
2 sig figs
4. 0.080
4. 0.080
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Significant Numbers in Calculations

• An answer cannot be more precise than the least
  precise measurement

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Adding and Subtracting

• The answer has the same number of decimal places
  as the measurement with the fewest decimal
  places.
• 25.2 one decimal place
• 1.34 two decimal places
• 26.54
• answer 26.5 one decimal place

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Learning Check

• In each calculation, round the answer to the
  correct number of significant figures.
• A. 235.05 19.6 2.1
• 1) 256.75 2) 256.8 3) 257
• B. 58.925 - 18.2
• 1) 40.725 2) 40.73 3) 40.7

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Multiplying and Dividing

• Round to the calculated answer until you have the
  same number of significant figures as the least
  precise measurement.

(13.91g/cm3)(23.3cm3) 324.103g
3 SF
4 SF
324 g
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Learning Check

• A. 2.19 X 4.2
• 1) 9 2) 9.2 3) 9.198
• B. 4.311 0.07
• 1) 61.58 2) 62 3) 60

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Percent Error

• Indicates accuracy of a measurement
• Formula on Reference Table T

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Percent Error

• A student determines the density of a substance
  to be 1.40 g/mL. Find the error if the
  accepted value of the density is 1.36 g/mL.

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DENSITY
13.6 g/cm3

• an important and useful physical property
• standard values can be found on Table S
• Density usually decreases as temperature
  increases because volume increases making the
  mass more spread out, but the total mass stays
  the same.
• One exception!! WATER
• Density decreases as the temperature decreases
  in water

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Density example

• An object has a volume of 825 cm3 and a density
  of 13.6 g/cm3. Find its mass.

GIVEN V 825 cm3 D 13.6 g/cm3 M ?
WORK M DV M (13.6 g/cm3)(825cm3) M 11,200
g
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Metric System

• 1. length
• The meter is the basic unit of length. The meter
  stick is divided into 100 equal parts each 1 cm
  in length
• 1km 103 micro meter 10-6 m
• 2. Mass
• The kilogram is the basic unit of mass
• 1kg is equal to the mass of 1L of water at 4 C
  therefore 1g of water equal to the volume of
  1cm3(ml) at 4 C
• 3. Volume
• The space occupied by matter. Derived from
  measurement of length.
• 1L 1000cm3 1ml 1cm3

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• Based on powers of 10

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SI Prefix Conversions(based on powers of 10)
http//www.emsc.nysed.gov/osa/reftable/chemistry-r
t/chemref1-7.pdf
Prefix
Symbol
Factor
move left
move right
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The Unit fraction Methodaka Dimensional
Analysis

• Steps
• 1. Identify starting ending units.
• 2. Line up conversion factors so units cancel.
• 3. Multiply all top numbers divide by each
  bottom number.
• 4. Check units answer.

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• set up
• known value with unit x unknown
  unit
• 
  known unit

Ex. 1 A rattlesnake is 2.44 m long. How long is
the snake in cm?
2.44 m x ______cm cm m
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Solution A rattlesnake is 2.44 m long. How
long is the snake in cm?

• 2.44 m x 100 cm 244 cm
• 1 m

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Write and solve for the following problems using
the factor label method

• 1) 20 cm to m
• 2) 500 ml to L
• 3) 0.032 L to mL
• 4) 45 m to km
• 5) 805 dm to km
• 6) 81 cm to mm
• 7) 5.29 cs to s
• 8) 3.78 kg to g

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Scientific Notation

• Scientific notation is a way of expressing really
  big numbers or really small numbers.

65,000 kg ? 6.5 104 kg
Move decimal until theres 1 digit to its left.
Places moved exponent. Large (gt1) ?
positive exponent Small (lt1) ? negative
exponent
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Graphs should contain the following features

• Independent variable in the X axis (with units)
• Dependent variable on the Y axis (with units).
• uniform numerical scale
• Include a title (Dependent Variable) vs.
  (Independent Variable)
• Data points, circled with point protectors.
• Data points connected with a line or a best fit
  line

Done on graph paper in pencil or on the computer