States of matter Solids and Liquids

L. Scheffler

Lincoln High School

Gases, Solids, and Liquids

Phase

Particle Properties

Spacing Energy Motion Volume Shape

Solid

Liquid

Gas

close low vibrational definite definite

close moderate rotational definite indefinite

far apart high translational indefinite indefinite

Other States of Matter

Amorphous Solids

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

Plasmas a. Hot, ionized gas particles. b. Electrically charged. c. Most common state in universe.

Chumbler - Properties of Matter4

Examples of Plasmas

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PlasmasMicroscopic 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 positively charged nuclei).

PHASE CHANGES

Description of Phase Change

Term for Phase ChangeHeat Movement During

Phase Change

Solid to liquid

MeltingHeat goes into the solid as it melts.

Liquid to solid

FreezingHeat leaves the liquid as it freezes.

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 CondensationHeat leaves the gas as it condenses.

Solid to gas SublimationHeat goes into the solid as it sublimates.

Heating CurvesThe temperature of most pure substances is constant during a phase change.

Cooling CurvesThe temperature of most pure substances is constant during a phase change.

Heat of FusionThe 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 fusion is 335 Joules per gram

Heat of VaporizationThe 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 generally much higher than the heat it takes to melt it.

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 warming effect

Vapor PressureVapor Pressure Explaining Vapor Pressure Explaining Vapor Pressure

on the Molecular Levelon the Molecular Level Dynamic Equilibrium: the point

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

Vapor pressure is the pressure exerted when the liquid and vapor are in dynamic equilibrium.

Vapor Pressure and the Vapor Pressure and the Boiling PointBoiling 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.

Normal boiling point is the boiling point at 760 torr (1 atm).

Gas-Liquid Equilibration

Vapor PressureVapor PressureVolatility, Vapor Pressure, and TemperatureVolatility, Vapor Pressure, and Temperature

Phase DiagramsPhase 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

gas.

Phase DiagramsPhase Diagrams Any temperature and pressure combination not

on a curve represents a single phase.

Phase DiagramA phase diagram shows the relationship between the three phases of matter

The boiling point of a substance depends on the pressure.

The melting point is not significantly affected by the pressure

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

At the triple point all three phases are in equilibrium

Phase Diagrams of HPhase Diagrams of H22O and O and COCO22 Water: The melting point curve slopes to the left because ice is

less dense than water. Triple point occurs at 0.0098C and 4.58 mmHg. Normal melting (freezing) point is 0C. Normal boiling point is 100C. Critical point is 374C and 218 atm.

Carbon Dioxide: Triple point occurs at -56.4C and 5.11 atm. Normal sublimation point is -78.5C. (At 1 atm CO2

sublimes it does not melt.) Critical point occurs at 31.1C and 73 atm.

Phase Diagrams of HPhase Diagrams of H22O & COO & CO22

Critical Pressure and Critical Pressure and TemperatureTemperature

Gases liquefied by increasing pressure at some temperature.

Critical temperature: the minimum temperature for liquefaction of a gas using pressure.

Critical pressure: pressure required for liquefaction.

Critical Temperature