Pearson Prentice Hall Physical Science: Concepts in Action

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Pearson Prentice Hall Physical Science Concepts
in Action

• Chapter 3
• States of Matter

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3.1 Solids, Liquids Gases

• Objectives
• 1. Explain how shape and volume can be used to
  classify materials
• 2. Describe how kinetic theory and forces of
  attraction can be used to explain the behavior of
  solids, liquids and gases

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How Shape Volume Classifies Materials

• Materials can be classified as solids, liquids,
  or gases based on whether their shapes and volume
  are definite or variable
• Definition a solid is the state in which
  materials have a definite shape and definite
  volume
• Definition definite means that shape and volume
  wont change unless the material is acted on by
  an outside force

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• Definition a liquid is the state of matter in
  which material has a definite volume but not a
  definite shape
• Liquids will take the shape of their container
• Definition a gas is the state of matter in which
  a material has no definite shape and no definite
  volume
• Gases will expand to completely fill the volume
  take the shape of their container

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• Almost all matter exists as a solid, liquid or
  gas on Earth
• This is not true for the universe
• In places with the temperature of stars, matter
  exists in a state called plasma
• In 1995, scientists discovered a fifth state of
  matter called BCE (Bose-Einstein condensate)
• At temperatures close to absolute zero (0 K or
  -273ºC), BCE groups of atoms behave as if they
  were a single particle

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Kinetic Theory

• Definition kinetic energy is the energy an
  object has due to its motion
• Kinetic theory says
• 1. That all particles of matter are in constant
  motion
• 2. There are forces of attraction among all
  particles of matter

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• Kinetic theory of gasses says
• 1. The constant motion of particles in a gas
  allows a gas to fill a container of any shape or
  size
• 2. Particles in a gas are in constant, rapid,
  random motion
• 3. The motion of 1 particle of gas is unaffected
  by other particles of gas unless they collide
• 4. Forces of attraction among particles of gas
  can be ignored under ordinary conditions

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• Kinetic theory of liquids says
• 1. A liquid takes the shape of its container
  because particles in a liquid can flow to new
  locations
• 2. The volume of a liquid is constant because
  forces of attraction keep particles close
  together
• Kinetic theory of solids says
• 1. Solids have a definite shape and volume
  because particles in a solid vibrate about a
  fixed point

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3.2 The Gas Laws

• Objectives
• 1. Explain what causes gas pressure in a closed
  container
• 2. Explain what factors affect gas pressure
• 3. Describe how temperature, volume and pressure
  of a gas are related

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Gas Pressure in Closed Containers

• Definition Pressure is the result of force
  distributed over an area
• The SI unit of pressure is the pascal (Pa)
• The SI unit of force is the newton (N)
• The unit for area is m2
• Since pressure force/area then Pa N/m2
• Collisions between particles of a gas and the
  walls of the container cause pressure in a closed
  container of gas

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Factors That Affect Gas Pressure Relationship
of Factors

• Three factors that affect gas pressure are
  temperature, volume and number of particles
• 1. Raising the temperature of a gas will increase
  its pressure if the volume of the gas and the
  number of the particles are held constant

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• 2. Reducing the volume of a gas increases its
  pressure if the temperature and number of gas
  particles is held constant
• 3. Increasing the number of particles will
  increase the pressure of a gas if the temperature
  and volume are constant

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3.3 Phase Changes

• Objectives
• 1. Explain six common phase changes
• 2. Describe what happens to a substances
  temperature systems energy during a phase
  change
• 3. Describe the arrangement of water molecules
  change during melting and freezing
• 4. Explain the difference between evaporation and
  boiling

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Six Common Phase Changes

• Definition a phase change is the reversible
  physical change that occurs when a substance
  changes from one state of matter to another
• Six common phase changes melting, freezing,
  vaporization, condensation, sublimation, and
  deposition

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Temperature, Energy Phase Changes

• The temperature of a substance does not change
  during a phase change
• For example, water temperature remains constant
  when boiling to go from liquid to gas or when
  condensing from a gas to liquid
• Q At what temperature does water boil and
  condense?

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• Energy is either absorbed or transferred during a
  phase change
• The amount of energy absorbed depends on the
  substance is a unique physical property for
  each substance
• Definition heat of fusion is the amount of
  energy absorbed when going from a solid to a
  liquid

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• Definition exothermic changes occur when energy
  is released to the environment
• An example of an exothermic change is water
  freezing since it releases its heat to the
  environment so that it can freeze
• Definition endothermic changes occur when energy
  is absorbed from the environment
• An example is water melting since it gathers as
  much heat as possible from the environment to melt

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Melting Freezing Water

• The arrangement of molecules in water becomes
  less orderly as water melts and more orderly as
  water freezes
• Solid water (ice) has molecules in a fixed
  position that vibrate about a fixed point
• Freezing produces molecules in an orderly
  arrangement
• Liquid water has molecules that are attracted to
  each other and slide past each other due to
  special chemical bonds
• Melting allows a less orderly molecular
  arrangement

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Evaporation Boiling

• Definition vaporization is a phase change from a
  liquid to a gas
• Vaporization is endothermic since liquid water
  absorbs energy in the form of heat from the
  surroundings to go from liquid to gas
• Definition heat of vaporization is the amount of
  energy needed for a substance to change phases
  from liquid to gas
• Heat of vaporization is a unique physical
  property for each substance

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• Definition evaporation is the process that
  changes a substance from a liquid to a gas below
  the substances boiling point
• Evaporation is a process that takes place at the
  surface of a liquid and occurs at temperatures
  below the boiling point
• Definition vapor pressure is the pressure caused
  by the collisions of vapor on the walls of the
  container
• Vapor pressure increases as temperature increases

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• Q How does surface area of a liquid affect the
  rate of evaporation?
• Definition the boiling point is where vapor
  pressure equals atmospheric pressure
• Kinetic theory shows that as the temperature
  increases, water molecules move faster faster
  until they have energy to overcome attractive
  forces of neighboring molecules
• Definition condensation is the phase change from
  a gas or vapor to a liquid

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• Definition sublimation is the phase change from
  solid to a gas without going through the liquid
  phase
• Example of sublimation is dry ice to CO2 at room
  temperature
• Definition deposition is the phase change from a
  gas or vapor to a solid without going through the
  liquid phase
• Deposition is the reverse of sublimation
• Example of deposition is frost on windows