INTRODUCTION and CHAPTER ONE

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1
INTRODUCTION
and
CHAPTER ONE
Read the Introduction and Chapter 1.
Chemistry is NOT a spectator sport.
Work out complete solutions for all
the bold numbered problems.
Welcome to the
World of
Chemistry
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Beginning Chemistry 200
• Read the book before class!
• Study the examples and do the
practice exercises.
• Be prepared for each class
session, lecture and laboratory.
• Don’t get behind.
4
Outline for Chapter 1
• Definitions
–Homogenous and Heterogeneous
–Matter ?
–3 states of matter
–Chemical –vs.- Physical Change
• Calculations
–Density
–Temperature
»Kelvin  Celsius  Fahrenheit
»Fahrenheit  Celsius  Kelvin
–Significant Figures (Sig Figs)
Matter
5
6
Mixtures
(a)Heterogeneous
(b)Suspension
(c)Homogenous
Cookie
Blood
Salt water
7
The Language of Chemistry
• CHEMICAL ELEMENTS
- pure
substances that cannot be decomposed by
ordinary means to other substances.
Aluminum
Bromine
Sodium
8
The Language of Chemistry
• The elements, their
names, and their
symbols are given
on the
PERIODIC
TABLE
• How many
elements are
there?
9
The Periodic Table
Dmitri Mendeleev (1834 - 1907)
10
Sodium
Find sodium, Na,
on the chart.
11
• An atom is the smallest particle of
an element that has the chemical
properties of the element.
Copper
atoms on
silica
surface.
Find copper on the chart.
12
The Atom
An atom consists of a nucleus (of protons
and neutrons) and electrons in space
about the nucleus.
Electron cloud
Nucleus
13
CHEMICAL COMPOUNDS
are composed of atoms and so can
be decomposed to those atoms.
The red compound is
composed of
• Ni- Nickel
• C- Carbon
• O- Oxygen
• N- Nitrogen
Fixed composition
14
MOLECULE
The smallest unit of a compound that
retains the chemical characteristics of
the compound.
MOLECULAR FORMULA
Composition of molecules
H2O
C8H10N4O2 - Caffeine
The Nature of Matter
Gold
Au
Mercury
Hg
Chemists are interested in the nature of
matter and how this is related to its atoms
and molecules.
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16
Graphite
layer
structure of
carbon
atoms
reflects
physical
properties.
17
Chemistry & Matter
• We can explore the MACROSCOPIC world
— what we can see —
• Understand the PARTICULATE world
— we cannot see —
We can write SYMBOLS to describe these worlds.
A Chemist’s View
Macroscopic
Particulate
Symbolic- 2 H2(g) + O2 (g) --> 2 H2O(g)
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19
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STATES OF MATTER
• SOLIDS — have rigid shape, fixed
volume. External shape can reflect the
atomic and molecular arrangement.
–Reasonably well understood.
• LIQUIDS — have no fixed shape and
may not fill a container completely.
–Not well understood.
• GASES — expand to fill their
container.
–Good theoretical understanding.
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THE THREE STATES OF
MATTER
Bromine (gas)
Aluminum (solid)
Water or H2O (liquid)
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KINETIC NATURE OF MATTER
Matter consists of atoms and molecules
in motion.
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Physical
Properties
What are some physical
properties?
–Color
–Melting and boiling
point
–Odor
–Conductivity
–Density
Physical Changes
Some physical changes
would be
– boiling of a liquid
– melting of a solid
– dissolving a solid in a
liquid to give a
homogeneous mixture
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DENSITY
- an important and useful
physical property
mass
(g)
Density =
volume (cm3)
Mercury
13.6 g/cm3
Gold
19.3 g/cm3
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Which is more dense?
27
Relative Densities of the Elements
28
Sig Figs
Sig Fig PPT
29
mass
(g)
Density =
volume (cm3)
Problem: A piece of
copper has a mass of
57.54 g. It is 9.36 cm
long, 7.23 cm wide,
and 0.95 mm thick.
Calculate density
(g/cm3).
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SOLUTION
1. Get dimensions in common units.
1cm
. mm •
= 0.095 cm3
0 95
10 mm
2. Calculate volume in cubic centimeters.
(9.36 cm)(7.23 cm)(0.095 cm) = 6.4 cm3
3.
Calculate the density.
6.4 cm3
= 9.0g/cm3
57.54g
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PROBLEM: Mercury (Hg) has a density
of 13.6 g/cm3. What is the mass of 95 mL
of Hg? In grams? In pounds?
Solve the problem using
DIMENSIONAL
ANALYSIS.
32
PROBLEM: Mercury (Hg) has a density
of 13.6 g/cm3. What is the mass of 95 mL
of Hg?
First, note that 1
cm3 = 1 mL
Then, use dimensional analysis to
calculate mass.
3
95 cm •
13.6 g
cm3
3
= 1.3 x 10 g
What is the mass in pounds?
See next slide
33
The milliliter
and the cubic
centimeter are
equivalent.
Notice the units
of 10’s.
back
34
PROBLEM: Mercury (Hg) has a density
of 13.6 g/cm3. What is the mass of 95 mL
of Hg?
What is the mass in pounds? (1 lb = 454 g)
1.3 x 103 g •
1 lb
= 2.8 lb
454 g
Density
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PROBLEM: An object weighing 15.67 g is
placed in water starting at 6.8 mL, then
displaces water to 20.2 mL. What is the
density of the object?
20.2
6.8
20.2mL - 6.8mL = 13.4mL
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PROBLEM: An object weighing 15.67 g is
placed in water starting at 6.8 mL, then
displaces water to 20.2 mL. What is the
density of the object?
1
3
15.67g
=
1.17g/cm
(20.2 - 6.8)ml
Chemical Properties and
Chemical Change
•Burning hydrogen (H2) in
oxygen (O2) gives H2O.
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Chemical Properties
• Similar to Physical Properties only
with reference to a Chemical
reactions
–Heat and or light produced
–Color
–Oder
Chemical Properties and
Chemical Change
• Burning hydrogen (H2) in
oxygen (O2) gives H2O.
• Chemical change or
chemical reaction
involves the
transformation of one or
more atoms or molecules
into one or more different
molecules.
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40
Chemical Change
2 Al + 3 Br2
Al2Br6
41
Electrolyzing water
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UNITS OF MEASUREMENT
• We make QUALITATIVE
observations of reactions —
changes in color and physical
state.
• We also make QUANTITATIVE
MEASUREMENTS, which involve
numbers.
• Use SI units — based on the
metric system
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UNITS OF MEASUREMENT
Use SI units — based on the
metric system
length
(meter, m)
mass
(kilogram, kg,
and gram, g)
time
(second)
Units of Length
• 1 kilometer (km) = ? meters (m)
• 1 meter (m) = ? centimeters (cm)
• 1 centimeter (cm) = ? millimeter (mm)
• 1 nanometer (nm) = 1.0 x 10-9 meter
O—H distance =
9.4 x 10-11 m
9.4 x 10-9 cm
0.094 nm
94 pm
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Measurement
• Learn the prefixes in Table 1.4
• Other Relationships
1 cm3 = 1 mL = 0.001 L
1.00 lb = 454 g
1.00 in = 2.54 cm
1.06 qt = 1.00 L
Significant figures Page 47
Precision and accuracy Page 43
Examples
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Temperature Scales
• Fahrenheit
• Celsius
• Kelvin
Anders Celsius
1701-1744
Lord Kelvin
(William Thomson)
1824-1907
Temperature Scales
Notice that 1 Kelvin degree = 1 degree Celsius
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Calculations Using
Temperature
• Generally require temp’s in Kelvin
• T (K) = t (°C) + 273
• Body temp = 37 oC + 273 = 310. K
• Liquid nitrogen = -196 oC + 273 = 77 K
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In Class Problems
• A rectangular box has dimensions of
20.0 cm  15.0 cm  8.00 mm. Calculate
the volume of the box in liters.
• A standard sheet of paper has dimensions
of 8.5 inch by 11 inch. A sheet of paper
weighs on the average 0.150 g and has a
density of 0.710 g/cm3. Calculate the
thickness of the paper in cm.
• A gallon (3.78 L) of latex paint can cover
385 ft2 of the surface of a wall. What is
the average thickness of one coat of paint
(in micrometers)?
Sample problems
• Calculate the volume of 525 g of
mercury, d=13.534g/cm3.
• The melting point of tin is 505.5 K.
Calculate the Celsius temperature.
• Find the symbol for gold and the
element name for K.
• An iron sheet is 3.50 cm square and
has a mass of 15.396 g. The density
of iron is 7.87 g/cm3. Calculate the
thickness of the iron sheet in mm.
The End!
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Dimensional Analysis
“English-English”
(one conversion)
1) 6 in = ? ft
6 in
1 ft
= 0.5 ft
12 in
2) 3.5 gal = ? qt
3.5 gal 4 qt
= 14 qt
1 gal
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Dimensional Analysis
“Metric-Metric”
(one conversion)
1) 5.0 cm = ? mm
5.0 cm 10 mm
= 50. mm
1 cm
2) 4.0 dg = ? kg
4.0 dg 1 kg
-4 kg
=
4.0
x
10
4
10 dg
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Dimensional Analysis
“Metric-English”
(one conversion)
1) 200.0 cm = ? in
200.0 cm 1.00 in
=
2.54 cm
78.74 in
2) 34 qt = ? L
34 qt 1.00 L =
1.06 qt
32 L
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Dimensional Analysis
“English-English” (two or more conversions)
1) 6 in = ? mile
6 in
1 mile
1 ft
12 in 5280 ft
=
9 x 10-5 mile
=
450 oz
2) 3.5 gal = ? oz
3.5 gal
4 qt 32 oz
1 gal 1 qt
55
Dimensional Analysis
“Metric-Metric” (two or more conversions)
1) 5.0 cm = ? km
5.0 cm 1 m
1 km
100cm 1000 m
= 5.0 x 10-5 km
2) 4 kg = ? pg
4 kg
103 g
1 kg
1012 pg
1g
=
4 x 1015 pg
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Dimensional Analysis
“Metric-English” (two or more conversions)
1) 200 m = ? in
200 m 100 cm 1.00 in
1 m
2.54 cm
=
8000 in
2) 34 qt = ? mL
34 qt
3 mL
10
1.00 L
1.06 qt 1 L
=
3.2 x 104 mL
57
Dimensional Analysis
“Derived Unit Conversions”
Area
1) 8.0 ft2 = ? cm2
8.0 ft2
2
2
144 in2 (2.54) cm
=
2
2
1.00
in
1 ft
7400 cm2
2) 2.3 cm2 = ? nm2
2.3 cm2 1014 nm2
1 cm2
= 2.3 x 1014 nm2
58
Dimensional Analysis
“Derived Unit Conversions”
Volume
1) 445 dm3 = ? mL
445 dm3 103 cm3 1 mL
1 dm3 1 cm3
= 4.45 x 105mL
2) 5 cm3 = ? mm3
5 cm3
103 mm3
1 cm3
=
5 x 103 mm3
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Dimensional Analysis
“Other Conversions Problems”
1) 100. km/hr = ? mile/hr
1 mile
100. km 105 cm 1.00 in 1 ft
1 km
5280 ft
hr
2.54 cm 12 in
= 62.1 mile/hr
2) 25 m/gal = ? nm/qt
25 m
gal
109 nm
1m
1 gal
4 qt
=
6.2 x 109 nm/qt
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Dimensional Analysis
“Other Conversions Problems” (continue)
3) Calculate the density of a material if 45
mL of it has a mass of 128 g.
128 g
= 2.8 g/mL
45 mL
4) Calculate the volume in mL of 2.5 g of a
material that has a density of 3.65 g/mL.
2.5 g
mL
3.65 g
=
0.68 mL
Dimensional Analysis
“Other Conversions Problems”
(continue)
5) Calculate the mass of 20 L of a material
that has a density of 8.54 g/mL.
20 L
103 ml
1L
8.54 g
ml
=
2 x 105 g
6) How many grams of gold are in 48 g of
an alloy that is 22.1% gold?
48 g alloy 22.1 g gold
=
100.0 g alloy
11 g gold
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Practice Problems
1) 6.45 m = ? cm
2) 12.4 kg = ? mg
3) 184 oz = ? g
4) 24 oz/hr = ? L/day
5) Determine the volume (in L) of 2 kg of sodium
chloride. (density = 2.17 g/mL)
6) How many grams of brass contain 50.0 g of
zinc? (This brass contains 15% Zn)
1) 645 cm 2) 1.24 x 107 mg 3) 5220 g 4) 17 L/day
5) 0.9 L 6) 330 g
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