Download - Copyright©2000 by Houghton Mifflin Company. All rights reserved. 1 Chapter 13 States of Matter Gases, Liquids and Solids

Copyright©2000 by Houghton Mifflin Company. All rights

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Chapter 13States of Matter

Gases, Liquids

and Solids


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Figure 10.1

Schematic Representations of the Three States of Matter


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• INDIVIDUAL MOLECULES FAR APART

• PARTICLES INTERACTING VERY LITTLE


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• MOLECULES ARE VIRTUALLY LOCKED IN PLACE

• CAN VIBRATE ABOUT THEIR POSITIONS

• VERY ORGANIZED


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• MOTION OF MOLECULES IS INCREASE

• GREATER MOVEMENT

• GREATER DISORDER


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Kinetic Molecular Theory

• Postulates

• A gas consists of a collection of small particles traveling in straight-line motion and obeying Newton's Laws.


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• Postulates

• The molecules in a gas occupy no volume (that is, they are points).


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• Postulates

• Collisions between molecules are perfectly elastic (that is, no energy is gained or lost during the collision).


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• Postulates

• There are no attractive or repulsive forces between the molecules.


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• Postulates

• The average kinetic energy of a molecule is

3/2 kT

• T is the absolute temperature.

• k is a constant


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• http://www.chm.davidson.edu/vce/kineticmoleculartheory/basicconcepts.html


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Liquids

• Particles in a liquid are attracted to each other.

• More dense than gases


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Some Properties of a Liquid

Surface Tension: The resistance to an increase in its surface area (polar molecules).

Capillary Action: Spontaneous rising of a liquid in a narrow tube.

Viscosity: Resistance to flow (molecules with large intermolecular forces).


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Liquids

• Conversion of a liquid to a gas is called vaporization.

• Evaporation versus Boiling?


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Surface Tension

• UNEVEN PULL OF MOLECULES AT THE SURFACE


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Figure 10.6

Molecules in a Liquid


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Liquids

• Vapor Pressure:

Measure of the force exerted by a gas above a liquid.

Increasing Temperature increases vapor pressure.


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Solids

• Generally described as

an orderly arrangement of particles

in fixed positions.


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Types of Solids

Crystalline Solids: highly regular arrangement of their components

Amorphous solids: considerable disorder in their structures (glass).


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Crystalline Solid

Lattice: A 3-D system of points designating the centers of components that make up the substance.


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Unit Cell

Smallest repeating unit of the lattice.


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Crystalline Solid

Unit Cell: The smallest repeating unit of the lattice.

Three common types:

simple cubic body-centered cubic face-centered cubic


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Figure 10.9

Three Cubic Unit Cells and the Corresponding Lattices


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Figure 10.12

Examples of Three Types of Crystalline Solids


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Allotropes

• Two or more different forms of the same element in the same physical state.

• Allotropes of carbon: diamond, graphite and buckminsterfullerene


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Diamond


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Graphite


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Buckminsterfullerene


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• http://preparatorychemistry.com/KMT.html


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To answer that we need to know more

about

Gas Pressure.


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Pressure

• Force per unit area

Pressure


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Gases.

The gas molecules are in constant motion, and sothey regularly hit the walls of the container.


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Gases.

The force of the gas molecules hitting the walls of the container is called the Gas Pressure.


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Gases.

The more gas molecules there are, the more often thewalls of the container are hit,

therefore the Gas Pressure is higher.


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Gases.

If the temperature (energy) of the gas is increased the molecules move faster and so hit the walls harder

causing the Gas Pressure to rise also.


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Measuring Pressure.

Vacuum. Vacuum.


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Measuring Pressure.

Vacuum.Gas Pressure.


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Measuring Pressure.



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Measuring Pressure.

Pressure is enough to push 20 cm/H2O………or 10 mm/Hg……..

Manometer.



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Spaceis a vacuum.

Atmosphere isa gas (Air).

Air moleculeshit the surface ofthe earth.


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Atmospheric Pressure

Pressure of the Airmolecules hitting

the earth.(or any other surfacein the atmosphere).

14 lbs. per square inch


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Atmospheric Pressure.

Patm = 760 mm/Hg (compared to a vacuum).


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We are so accustomed to Atmospheric Pressure that we forget its there.


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Atmospheric Pressure = Weight of the Air

Results from the mass of the air beingpulled toward the center of the earth by GRAVITY.

Measures using a barometer.


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Figure 5.2A Torricellian Barometer

At sea level =760 mm Hg

At elevation of 9600 feet =

520 mm Hg


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Pressure

is equal to force/unit area

SI units = Newton/meter2 = 1 Pascal (Pa)

1 standard atmosphere = 101,325 Pa

1 standard atmosphere = 1 atm =

760 mm Hg = 760 torr


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Pressure Units

• 1 atmosphere (atm)= 760 mm Hg= 760 torr= 101,325 Pa= 29.92 inch Hg= 14.7 lb/ in2 (psi)


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CHANGES OF STATE (PHASE TRANSISTIONS)

1) MELTING: s l

2) FREEZING: l s

3) VAPORIZATION: l g

4) SUBLIMATION: s g

5) CONDENSATION: LIQUEFACTION: g lDEPOSITION: g s


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PHASE DIAGRAMS

• GRAPHICAL WAY TO SUMMARIZE THE PHASES OF A SUBSTANCE AS A FUNCTION OF TEMPERATURE ANE PRESSURE

• DIAGRAMS NOT DRAWN TO SCALE


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The Phase Diagram for Water


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Figure 10.52

The Phase Diagram for Carbon Dioxide


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TRIPLE POINT

• REPRESENTS TEMPERATURE AND PRESSURE AT WHICH 3 PHASES OF A SUBSTANCE COEXIST IN EQUILIBRIUM

• FOR WATER,– 0.016 °C, 0.00603 atm (0.61 kPa).


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CRITICAL POINT

• CRITCAL TEMPERATURE:TEMPERATURE ABOVE WHICH

THE VAPOR CANNOT BE LIQUEFIED NO MATTER WHAT PRESSURE IS APPLIED

• CRITICAL PRESSURE:VAPOR PRESSURE AT THE

CRITICAL TEMPERATURE• WATER: 374°C, 218 atm.

Download - Copyright©2000 by Houghton Mifflin Company. All rights reserved. 1 Chapter 13 States of Matter Gases, Liquids and Solids

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