CHM 103 Lecture 4 S07

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Transcript CHM 103 Lecture 4 S07

Announcements & Agenda (01/17/07)
Office Hours cancelled today (Red Wings)
CD quizzes due NOW
Quiz 2 today!
See overhead for your clicker number
You should currently be reading Ch 3 
Today:
 Finish Heating/Cooling Curves (Ch 2)
 Classification of Matter (3.1)
 Elements, Atoms, & Subatomic Particles (3.2-3.5)
1
Last Time: Heat Energy
Heat = mass x DT x (Specific Heat)
The amount of heat lost or gained by a substance is
calculated from the
• mass of substance (g).
• temperature change (DT).
• specific heat of the substance (J/g°C).
Key Point: If one substance “heats up” by a certain
amount, another substance must exactly lose that same
amount of heat!
2
Last Time: Phases Changes
deposition
melting
sublimation
(e.g. freeze-drying)
freezing
condensation
vaporization
3
Last Time: Heat of Fusion/Vaporization
Measure of heat energy released/absorbed
during the appropriate phase change for 1 g of
substance
Water: Heat of fusion @ MP = 80. cal
1 g water
Water: Heat of vaporization @ BP = 540. cal
1 g water
4
Summary of Heating Processes:
Heating Curves
A heating curve
• illustrates the
changes of state as
a solid is heated.
• uses sloped lines to
show an increase in
temperature.
• uses plateaus (flat
lines) to indicate a
change of state.
5
Cooling Curve
Using the heating curve of water as a guide,
draw a cooling curve for water beginning with
steam at 110°C and ending at -20°C.
6
Combined Heat Calculations
To reduce a fever, an infant is packed in 250. g of ice.
If the ice (at 0°C) melts and warms to body
temperature (37.0°C), how many calories are
removed from the body?
Step 1: Diagram the changes
DT = 37.0°C - 0°C = 37.0°C
37°C
temperature increase
0°C
solid
liquid
melting
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Combined Heat Calculations
(continued.)
Step 2: Calculate the heat to melt ice (fusion)
250. g ice x 80. cal
= 2.000  104 cal
1 g ice
Step 3: Calculate the heat to warm the water from
0°C to 37.0°C (SH of water = 1 cal/g)
250. g x 37.0°C x 1.00 cal = 9 250 cal
g °C
Total: Step 2 + Step 3
= 29 200 cal
(rounded to 3 SF)
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29 Good Practice Problems (Ch 3)
3.03, 3.05, 3.07, 3.11, 3.15, 3.17,
3.19, 3.23, 3.29, 3.35, 3.37, 3.41,
3.49, 3.51, 3.55, 3.59, 3.65, 3.67,
3.69, 3.73, 3.77, 3.79, 3.81, 3.85,
3.91, 3.95, 3.97, 3.101, 3.103
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Chemistry: The Study of the
Properties & Behavior of Matter
Pure substance: matter with fixed/definite composition
Elements: substance composed of only one type of atom
Compounds: combination of 2 or more elements in same
ratio (e.g. water, carbon dioxide, sodium chloride)
Mixtures: two or more substances that can be
separated by physical means
Heterogeneous mixtures: non-uniform distribution of
substances (e.g. mud = sand and saltwater, chocolate chip
cookie)
Homogenous mixtures: uniform distribution of substances
(e.g. saltwater = salt and water, air, Kool Aid)
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Visual Summary
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Elements
 Pure substances that cannot be separated into
different substances by chemical processes
 Are the building blocks of matter (the ABCs)
 112 elements known today
Examples:
carbon
gold
calcium
12
Symbols of Elements
 Use 1 or 2 letter abbreviations
 Capitalize the first letter only
Examples:
C carbon
N nitrogen
F fluorine
O oxygen
Co cobalt
Ca calcium
Br bromine
Mg magnesium
13
Symbols from Latin Names
Element
Copper
Gold
Lead
Mercury
Potassium
Silver
Sodium
Tin
Symbol
Cu
Au
Pb
Hg
K
Ag
Na
Sn
Latin name
cuprum
aurum
plumbum
hydrargyrum
kalium
argentum
natrium
stannum
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% Major Elements in the Body
(Know These!)
O 65.0 %
C 18.0
H 10.0
N 3.0
Ca 1.4
P 1.0
Mg 0.50
K
S
Na
Cl
Fe
Zn
0.34
0.26
0.14
0.14
0.004
0.003
Trace Elements
As, Cr, Co, Cu, F, I, Mn, Mo, Ni, Se, Si, V
15
Dalton’s Atomic Theory
 Atoms are building blocks of elements
 Similar atoms in each element
 Different from atoms of other elements
 Two or more different atoms bond in simple
ratios to form compounds
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Conservation Laws
1. Atoms are conserved during physical
and chemical transformations
– atoms are neither created nor destroyed
during a chemical or physical process
2. Mass is conserved during physical and
chemical transformations
– mass is neither created nor destroyed
during a chemical or physical process
3. Charge is also conserved during
physical and chemical transformations
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Methane (CH4) reacts with oxygen (O2) to produce carbon
dioxide (CO2) and water (H2O). COUNT THE ATOMS!
SEE BOB DEMO!
18
Subatomic Particles
Atoms contains subatomic particles,
• protons have a positive (+) charge.
• electrons have a negative (-) charge.
• like charges repel and unlike charges
attract.
• neutrons are neutral.
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Structure of the Atom
• dense nucleus that
contains protons and
neutrons.
• of electrons in a
large empty space
around the nucleus.
20
Atomic Mass Scale
On the atomic mass scale for subatomic particles,
• 1 atomic mass unit (amu) has a mass equal to 1/12 of
the mass of the carbon-12 atom.
• a proton has a mass of about 1 (1.007) amu.
• a neutron has a mass of about 1 (1.008) amu.
• an electron has a very small mass, 0.000549 amu.
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Summary
22
Atomic Number = The Identity of
the Element
Counts the number
of
protons
in an atom
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All Atoms of the Same Element
Have the Same # of Protons!!!
11 protons
Symbol
11
Na
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www.webelements.com
25
Mass Number
Since protons and neutrons account for most
of the mass of the atom,
count the number
of
protons and neutrons
to determine the mass number!!!
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Nuclear Symbol
• represents a particular atom of an element.
• gives the mass number in the upper left corner
and the atomic number in the lower left corner.
Example: An atom of sodium with atomic
number 11 and a mass number 23 has the
following atomic symbol:
mass number
23
Na
atomic number
11
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Electrons in An Atom
An atom of
• an element is electrically neutral; the net charge of
an atom is zero.
• has an equal number of protons and electrons.
number of protons = number of electrons
Aluminum has 13 protons and 13 electrons. The net
charge is zero.
13 protons (13+) + 13 electrons (13 -) = 0
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