Introductory Chemistry:

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Introductory Chemistry
Chapter 1

• Chemistry and You

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Lab Safety SymbolsIdentify the following symbols
A. B. C. D. E. F. G. H. I.
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• What is the definition of chemistry?
• Study of all substances and the changes they
  undergo.

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Learning Chemistry

• Different people learn chemistry differently.
• What do you see in the picture?
• Some people see a vase on a dark background, some
  people see two faces.

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Problem Solving

• Connect the 9 dots using only four straight lines.

• Experiment until you find a solution.
• However, we have used 5 straight lines.
• No matter which dot we start with, we still need
  5 lines.

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Problem Solving

• Are we confining the problem?

• We need to go beyond the 9 dots to answer the
  problem.

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Chemistry The Central Science

• Why????
• Most other sciences demand an understanding of
  basic chemical principles, and Chemistry is often
  referred to as the Central Science

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Modern Chemistry

• Chemistry is a science that studies the
  composition of matter and its properties.
• Chemistry is divided into several branches
• Organic chemistry is the study of substances
  containing carbon
• Inorganic chemistry is the study of all other
  substances that dont contain carbon
• Biochemistry is the study of substances derived
  from plants and animals
• Analytical is the study of matter and ways to
  study the properties of matter.
• Physical is the physics of chemistry.
  Thermodynamics and quantum mechanics.

Chapter 1
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The Standard Units

• Scientists have agreed on a set of international
  standard units for comparing all our measurements
  called the SI units

Quantity Unit Symbol
length meter m
mass kilogram kg
time second s
temperature kelvin K
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Length

• SI unit meter
• About a yard
• Commonly use centimeters (cm)
• 1 m 100 cm
• 1 cm 0.01 m 10 mm
• 1 inch 2.54 cm

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Mass

• Measure of the amount of matter present in an
  object
• weight measures the gravitational pull on an
  object, which depends on its mass
• SI unit kilogram (kg)
• about 2 lbs. 3 oz.
• Commonly measure mass in grams (g) or milligrams
  (mg)

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Time

• measure of the duration of an event
• SI units second (s)

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Temperature Scales

• Fahrenheit Scale, F
• used in the U.S.
• Celsius Scale, C
• used in all other countries
• Kelvin Scale, K
• The SI unit for temperature

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Prefix Multipliers in the SI System
Prefix Symbol Decimal Equivalent Power of 10
mega- M 1,000,000 Base x 106
kilo- k 1,000 Base x 103
deci- d 0.1 Base x 10-1
centi- c 0.01 Base x 10-2
milli- m 0.001 Base x 10-3
micro- m 0.000 001 Base x 10-6
nano- n 0.000 000 001 Base x 10-9
pico p 0.000 000 000 001 Base x 10-12
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What Is a Measurement?

• quantitative observation
• every measurement has a number and a unit
• every digit written is certain, except the last
  one which is estimated

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Estimation in Weighing

• What is the uncertainty in this reading?

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Uncertainty in Measured Numbers

• uncertainty comes from
• limitations of the instruments used for
  comparison,
• the experimental design,
• the experimenter,
• natures random behavior

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Precision and Accuracy

• accuracy is an indication of how close a
  measurement comes to the actual value of the
  quantity
• precision is an indication of how reproducible a
  measurement is

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Accuracy vs. Precision
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Precision

• imprecision in measurements is caused by random
  errors
• errors that result from random fluctuations
• we determine the precision of a set of
  measurements by evaluating how far they are from
  the actual value and each other
• even though every measurement has some random
  error, with enough measurements these errors
  should average out Do multiple trials!

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Accuracy

• inaccuracy in measurement caused by systematic
  errors
• errors caused by limitations in the instruments
  or techniques or experimental design
• we determine the accuracy of a measurement by
  evaluating how far it is from the actual value
• systematic errors do not average out with
  repeated measurements because they consistently
  cause the measurement to be either too high or
  too low

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Volume

• Derived unit
• any length unit cubed
• Measure of the amount of space occupied
• SI unit cubic meter (m3)
• Commonly measure solid volume in cubic
  centimeters (cm3)
• 1 m3 106 cm3
• 1 cm3 10-6 m3 0.000001 m3
• Commonly measure liquid or gas volume in
  milliliters (mL)
• 1 L is slightly larger than 1 quart
• 1 L 1 dm3 1000 mL 103 mL
• 1 mL 0.001 L 10-3 L
• 1 mL 1 cm3

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Mass Volume

• mass and volume are extensive properties
• the value depends on the quantity of matter
• extensive properties cannot be used to identify
  what type of matter something is
• if you are given a large glass containing 100 g
  of a clear, colorless liquid and a small glass
  containing 25 g of a clear, colorless liquid -
  are both liquids the same stuff?

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Mass vs. Volume of Brass
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Significant Figures

• the non-place-holding digits in a reported
  measurement are called significant figures
• significant figures tell us the range of values
  to expect for repeated measurements

12.3 cm has 3 sig. figs. and its range is 12.2
to 12.4 cm
12.30 cm has 4 sig. figs. and its range is 12.29
to 12.31 cm
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Counting Significant Figures

• All non-zero digits are significant
• 1.5 has 2 sig. figs.
• Interior zeros are significant
• 1.05 has 3 sig. figs.
• Leading zeros are NOT significant Pacific Ocean
  side
• 0.001050 has 4 sig. figs.
• 1.050 x 10-3

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Counting Significant Figures

• Trailing zeros may or may not be significant
  Atlantic Ocean Side
• Trailing zeros after a decimal point are
  significant
• 1.050 has 4 sig. figs.
• Zeros at the end of a number without a written
  decimal point are ambiguous and should be avoided
  by using scientific notation
• if 150 has 2 sig. figs. then 1.5 x 102
• but if 150 has 3 sig. figs. then 1.50 x 102

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Determining the Number of Significant Figures in
a Number
How many significant figures are in each of the
following? 0.04450 m 5.0003 km 1.000 105
s 0.00002 mm 10,000 m
4 sig. figs. the digits 4 and 5, and the
trailing 0
5 sig. figs. the digits 5 and 3, and the
interior 0s
4 sig. figs. the digit 1, and the trailing 0s
1 sig. figs. the digit 2, not the leading 0s
Ambiguous, generally assume 1 sig. fig.
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Multiplication and Division with Significant
Figures

• when multiplying or dividing measurements with
  significant figures, the result has the same
  number of significant figures as the measurement
  with the fewest number of significant figures
• 5.02 89,665 0.10 45.0118 45
• 3 sig. figs. 5 sig. figs. 2 sig. figs.
  2 sig. figs.
• 5.892 6.10 0.96590 0.966
• 4 sig. figs. 3 sig. figs. 3 sig.
  figs.

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Addition and Subtraction with Significant Figures

• when adding or subtracting measurements with
  significant figures, the answer should reflect
  the largest uncertainty.
• 5.74 0.823 2.651 9.214 9.21
• 3 sf. 3 sf. 4 sf. 3 sf
• 4.8 - 3.965 0.835 0.8
• 2sf 4sf.
  2sf

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Rounding

• if the number after the place of the last
  significant figure is
• 0 to 4, round down
• drop all digits after the last sig. fig. and
  leave the last sig. fig. alone
• add insignificant zeros to keep the value if
  necessary
• 5 to 9, round up
• drop all digits after the last sig. fig. and
  increase the last sig. fig. by one
• add insignificant zeros to keep the value if
  necessary
• to avoid accumulating extra error from rounding,
  round only at the end, keeping track of the last
  sig. fig. for intermediate calculations

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Rounding

• rounding to 2 significant figures
• 2.34 rounds to 2.3
• 2.37 rounds to 2.4
• 2.349865 rounds to 2.3

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Rounding

• rounding to 2 significant figures
• 0.0234 rounds to 0.023
• 0.0237 rounds to 0.024
• 0.02349865 rounds to 0.023

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Rounding

• rounding to 2 significant figures
• 234 rounds to 230 or 2.3 102
• 237 rounds to 240 or 2.4 102
• 234.9865 rounds to 230 or 2.3 102

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Both Multiplication/Division and
Addition/Subtraction with Significant Figures

• do whatever is in parentheses first,
• First, evaluate the significant figures in the
  parentheses
• Second, do the remaining steps
• 3.489 (5.67 2.3)
• 3 dp 2 dp
• 3.489 3.3 12
• 4 sf 2 sf 2 sf

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Example 1.6 Perform the following calculations
to the correct number of significant figures
b)
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Example 1.6 Perform the following calculations
to the correct number of significant figures
b)
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Density

• Ratio of massvolume
• Solids g/cm3
• 1 cm3 1 mL
• Liquids g/mL
• Gases g/L
• Volume of a solid can be determined by water
  displacement Archimedes Principle

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Density

• Density solids gt liquids gtgtgt gases
• except ice is less dense than liquid water!
• Heating an object generally causes it to expand,
  therefore the density changes with temperature

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Density

• Iron has a density of 7.86 g/cm3. Could a block
  of metal with a mass of 18.2 g and a volume of
  2.56 cm3be iron?

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Density

• What volume would a 0.871 g sample of air occupy
  if the density of air is 1.29 g/L?

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Units

• Always write every number with its associated
  unit
• Always include units in your calculations
• you can do the same kind of operations on units
  as you can with numbers
• cm cm cm2
• cm cm cm
• cm cm 1
• using units as a guide to problem solving is
  called dimensional analysis

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Problem Solving and Conversion Factors

• Conversion factors are relationships between two
  units
• May be exact or measured
• Conversion factors generated from equivalence
  statements
• e.g., 1 inch 2.54 cm can give or

METRIC TO ENGLISH CONVERSION ON PAGE 936 IN YOUR
TEXT BOOK
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Dimensional Analysis

• Using units as a guide to problem solving is
  called dimensional analysis
• This is the technique that we have learned to
  convert between two different units.

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Problem Solving and Dimensional Analysis

• Arrange conversion factors so given unit cancels
• Arrange conversion factor so given unit is on the
  bottom of the conversion factor
• May string conversion factors
• So we do not need to know every relationship, as
  long as we can find something else the given and
  desired units are related to

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Practice Convert 154.4 lbs to kg(1 kg 2.20
lbs)
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Practice Convert 30.0 mL to quarts(1 L 1.057
qt)
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How many cubic centimeters are there in 2.11 yd3?
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Practice 1.9 Convert 2.11 yd3 to cubic
centimeters
Sort information Given Find 2.11 yd3 volume, cm3
Strategize Concept Plan Relationships 1 yd 36 in 1 in 2.54 cm
Follow the concept plan to solve the problem Solution
Sig. figs. and round Round 1613210.75 cm3 1.61 x 106 cm3
Check Check Units magnitude are correct
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Impossible Conversions

• Is it possible to find how many seconds in a
  kilogram?
• In order to do unit conversions they must be able
  to correspond to the same quantity.
• For example, kilograms and pounds are both units
  of mass.

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Graphing in Science

• All graphing that is done in science must include
  the following
• A descriptive title
• X and Y axis labeled with units.
• The X axis is the manipulated variable and the
  Y- axis is the responding variable.
• A trend line (or line of best fit) to show the
  trend in the data that has been plotted.

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Convert 30.0 mL to quarts
154.4 lbs Lbs to kg
Given Find

• Sort information

1 L 1.057 qt 1 L 1000 mL
Concept Plan Relationships

• Strategize

Solution

• Follow the concept plan to solve the problem

0.03171 qt 0.0317 qt
Round

• Sig. figs. and round

Units magnitude are correct
Check

• Check

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Scientific Investigations

• Science is the methodical exploration of nature
  followed by a logical explanation of the
  observations.
• Scientific investigation entails
• planning an investigation
• carefully recording observations
• gathering data
• analyzing the results

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The Scientific Method

• The scientific method is a systematic
  investigation of nature and requires proposing an
  explanation for the results of an experiment in
  the form of a general principle.
• The initial, tentative proposal of a scientific
  principle is called a hypothesis.
• After further investigation, the original
  hypothesis may be rejected, revised, or elevated
  to the status of a scientific principle.

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Scientific Method
a test of a hypothesis or theory
a tentative explanation of a single or small
number of natural phenomena
a general explanation of natural phenomena
the careful noting and recording of natural
phenomena
a generally observed natural phenomenon
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Conclusions Continued

• After sufficient evidence, a hypothesis becomes a
  scientific theory.
• A natural law is a measurable relationship.

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Conclusions

• Scientists use the scientific method to
  investigate the world around them.
• Experiments lead to a hypothesis, which may lead
  to a scientific theory or a natural law.
• Chemistry is a central science with many
  branches.
• The impact of chemistry is felt in many aspects
  of our daily lives.

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QUIZE - CHAPTER -1

• What is the difference between a hypothesis and
  theory
• According to the ancient Greeks, which of the
  following are not basic elements found in nature
• Air
• Coal
• Fire
• Earth
• Gold
• Water