StatesMatterPPT

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Gases, Solids, and Liquids

Phase

Particle Properties

Spacing Energy Motion Volume Shape

Solid Liquid

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Other States of Matter

Amorphous Solids

Most solids with particles in repeating geometric patterns are crystals. Those with particles

arranged randomly are amorphous. Glasses are one type of amorphous solid

Plasmas

a. Hot, ionized gas particles. b. Electrically charged.

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Plasmas

Microscopic Explanation for Properties of Plasmas

 Plasmas have an indefinite shape and an

indefinite volume because the particles can move past one another.

 Plasmas are easily compressible because

there is a great deal of free space between particles.

 Plasmas are good conductors of

electricity and are affected by magnetic fields because they are composed of ions (negatively charged electrons and

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PHASE CHANGES

Description of

Phase Change Term for Phase Change

Heat Movement During Phase Change

Solid to

liquid

Melting

Heat goes into

the solid as it

melts.

Liquid to

solid

Freezing

Heat leaves the

liquid as it

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PHASE CHANGES

Description of Phase Change

Term for Phase Change

Heat Movement During Phase Change

Liquid to gas

Vaporization, which includes boiling and

evaporation

Heat goes into the liquid as it vaporizes.

Gas to liquid Condensation Heat leaves the gas as

it condenses.

Solid to gas Sublimation Heat goes into the

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Heating Curves

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Cooling Curves

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Heat of Fusion

The heat required to convert a substance from the solid to the

liquid phase is known as the heat of fusion

The heat of fusion is a property of the

substance.

For water the heat of

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Heat of Vaporization

The heat required to convert a substance

from the liquid to the gas phase is known as the heat of vaporization

The heat of vaporization for a substance depends on the temperature

For water the heat of vaporization is about 2240 Joules per gram

The heat required to

vaporize a substance is

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Evaporation

• The molecular velocities of the particles in the liquid phase vary according to a Maxwell-Boltzman distribution

• The faster moving particles at the surface may escape the confines of the liquid entirely.

• Some particles in the vapor phase may be recaptured by the liquid.

• Since the higher energy particles are more likely to escape the average energy of the liquid particles is reduced.

• Evaporation is a cooling effect, while condensation is a

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Vapor Pressure

Explaining Vapor Pressure

on the Molecular Level

 Dynamic Equilibrium: the point

when as many molecules escape the surface as strike the surface.

 Vapor pressure is the pressure

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Vapor Pressure and the

Boiling Point

 Liquids boil when the external pressure equals the vapor

pressure.

 The vapor pressure of a liquid increases with temperature  The temperature of boiling point increases as pressure

increases.

 There are two ways to get a liquid to boil: increase

temperature or decrease pressure.

 Pressure cookers operate at high pressure. At high

pressure the boiling point of water is higher than at 1 atm. Therefore, there is a higher temperature at which the

food is cooked, reducing the cooking time required.

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Vapor Pressure

Volatility, Vapor Pressure, and

Temperature

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Phase Diagrams

 A Phase Diagram is a graph of pressure vs. Temperature

summarizing all equilibria between phases.

 Given a temperature and pressure, phase diagrams tell us

which phase(s) will exist.

 Key Features of a phase diagram:

 Vapor-pressure curve: generally as pressure increases,

temperature increases.

 Melting point curve: as pressure increases, the solid

phase is favored if the solid is more dense than the liquid

Triple point: temperature and pressure at which all three phases are in equilibrium.

 Normal boiling and melting points (I.e. at 1 atm)

 Critical point: critical temperature and pressure for the

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Phase Diagrams

 Any temperature and pressure combination not

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Phase Diagram

A phase diagram shows the relationship between the three phases of matter

The boiling point of a substance depends on the pressure.

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Phase Diagram

The boiling point of a liquid is the temperature at which the vapor pressure of the liquid is equal to atmospheric

pressure

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Phase Diagram of H

₂₂

O

 The melting point curve slopes

to the left because ice is less dense than water.

 Triple point occurs at 0.0098C

and 4.58 mmHg.

 Normal melting (freezing) point

is 0C.

 Normal boiling point is 100C.  Critical point is 374C and 218

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Phase Diagram of CO

₂₂

Carbon Dioxide:

 Triple point occurs at

-56.4C and 5.11 atm.

 Normal sublimation point

is -78.5C. (At 1 atm CO₂ sublimes it does not melt.)

 Critical point occurs at

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Critical Temperature

and Critical Pressure

Gases liquefied by increasing pressure at some temperature.

 Critical temperature: the minimum temperature for

liquefaction of a gas using pressure.

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Specific Heat



The ability of a material to absorb and

release heat depends on its composition

and makeup



The heat required to raise the

temperature of 1 gram of a material 1

o

C is

called the

specific heat.

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Phase Change

--Problem 1

Problem 1

20.0 g of ice at -10.0oC is heated until it melts and the is

further heated to a final temperature of 40.0oC. Calculate

the total heat change for the ice. The heat of fusion of ice is 335 Jg-1. The specific heat of ice is 2.05 Jg-1 oC-1 and

that of liquid water is 4.18 J g-1 oC-1 _.

Q = (20.0g)(10.0oC)(2.05 Jg-1 oC-1)+ (20.0g)(335 J g-1) + (20.0g)(4.18J g-1 oC-1)(40.0oC)

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Phase Change –

Problem 2

50.0 g of water at 12.0oC is added to 120.0 g of water

at 84.0 oC. Calculate the final temperature of the

water

.

Let T = final temperature Then

(50.0g x (T- 12.0 oC)(4.18Jg-1 oC-1) =(120g)(84.0 oC -T)(4.18Jg-1 oC-1) 50T-600 = 10080 – 120 T