A Macroscopic Description of Matter

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A Macroscopic Description of Matter
Readings Chapter 16
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Solid, Liquid, Gas

• Solid has well-defined shape and well-defined
  surface. Solid is (nearly) incompressible.
• Liquid has well-defined surface (not shape), It
  is (nearly) incompressible.
• Gases are compressible. They occupy all volume.

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Solid, Liquid, Gas Density

• Density is defined as a ratio of the mass of the
  object and occupied volume
• The mass of unit volume (1m x 1m x 1m)
• Units

The density of the ice is slightly less than
water, causing them to float. Roughly 9/10 of the
iceberg is below water.
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Solid, Liquid, Gas Density
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At 4C water expands on heating or cooling. This
density maximum together with the low ice density
results in (i) the necessity that all of a body
of fresh water (not just its surface) is close to
4C before any freezing can occur, (ii) the
freezing of rivers, lakes and oceans is from the
top down, so permitting survival of the bottom
ecology.
atmospheric pressure
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Solid, Liquid, Gas Mole
1 mole (1 mol) of substance is an amount which
contains basic particles
(atoms or molecules) Avogadros number is the
number of basic particles in 1 mole
If we know the number n of protons and neutrons
in basic particles then we can find the mass of 1
mole
So, n is the molar mass (the mass of 1 mole in
grams)
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The number of protons and neutrons in atom
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Temperature

• Temperature is the measure of internal thermal
  energy
• Different scale
• - Fahrenheit, F
• Celsius, C
• Kelvin, K - SI scale of
  temperature

Example
Absolute zero
The temperature (in K) can be only positive
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Solid, Liquid, Gas Phase Changes
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Heat Specific Heat
Specific heat of a substance is related to its
thermal energy. Specific heat is defined as The
amount of energy that raises the temperature of 1
kg of a substance by 1 K is called specific heat,
c.
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Phase Change Solid, Liquid, and Gas
Phase change change of thermal energy without a
change in temperature
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Phase Change Solid, Liquid, and Gas
Phase change change of thermal energy without a
change in temperature
Specific Heat
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Phase Change Solid, Liquid, and Gas
Phase change change of thermal energy without a
change in temperature
Heat of transformation (L) the amount of heat
energy that causes 1 kg of a substance to undergo
a phase change.
Heat of Fusion
Heat of Vaporization
Heat of Fusion the heat of transformation
between a solid and a liquid
Heat of Vaporization the heat of transformation
between a liquid and a gas
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Specific Heat
Heat of Transformation
Substance Specific HeatJ/kg/K
Water (0 oC to 100 oC) 4186
Methyl Alcohol 2549
Ice (-10 oC to 0 oC) 2093
Steam (100 oC) 2009
Benzene 1750
Wood (typical) 1674
Soil (typical) 1046
Air (50 oC) 1046
Aluminum 900
Marble 858
Glass (typical) 837
Iron/Steel 452
Substance Latent HeatFusionkJ/kg MeltingPointC Latent HeatVaporizationkJ/kg BoilingPointC
Alcohol, ethyl 108 -114 855 78.3
Ammonia 339 -75 1369 -33.34
Carbon dioxide 184 -78 574 -57
Helium     21 -268.93
Hydrogen 58 -259 455 -253
Lead 24.5 372.3 871 1750
Nitrogen 25.7 -210 200 -196
Oxygen 13.9 -219 213 -183
Water 334 0 2260 (at 100oC) 100
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Ideal Gas
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Ideal Gas

• Ideal gas
• no interactions between the atoms, (without
  interactions no phase transition to liquid phase)
• atom as a hard-sphere
• temperature will determine the average speed of
  atoms.

Boltzmanns constant
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Ideal-Gas Law
p gas pressure V gas volume (container
volume) T gas temperature (in Kelvin!!) n the
number of moles this can be found as
where M is the mass of the gas
and is the mole mass R8.31 J/mol
K - universal gas constant
gas
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Ideal-Gas Processes
The state of the gas is determined by two
parameters P and V or P and T or V and T
If we know P and V then we can find T pV diagram
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Ideal-Gas Processes Constant Volume Process
V constant
Isochoric process
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Ideal-Gas Processes Constant Pressure Process
p constant
Isobaric process
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Ideal-Gas Processes Constant Temperature Process
T constant
Isothermal process
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Example Find , and
if n 3 mol
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Example Find , and
if n 3 mol