Phase Changes

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Phase Changes

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Change of Phase

• Is the conversion of a substance from one
  physical form to another

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Phases of Matter

• Melting
• Freezing
• Vaporization
• Condensation
• Sublimation
• Deposition

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Melting

• Is the phase change from a solid to a liquid
• Endothermic change-absorbs energy
• Melting pointis the temperature at which the
  substance changes from a solid to a liquid
• 0ºC

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Freezing

• Is the phase change from a liquid to a solid.
• Freezing point is the temperature at which this
  occurs
• Freezing is an exothermic change because energy
  is being taken out of the substance during this
  phase change
• It is the reverse process of melting , they occur
  at the same temperature 0ºC

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Vaporization

• Is the phase change from a liquid to a gas
• Boiling
• Evaporation

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Boiling

• Is vaporization that occurs throughout a liquid
• Boiling point the point at which a liquid boils
• Water boils at 100ºC

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Evaporation

• Is vaporization that occurs at the surface of a
  liquid
• Endothermic change
• Liquid water vaporizes into steam at 100ºC

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Condensation

• The phase change from a gas to a liquid
• It is an exothermic change.

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Sublimation

• The phase change from a solid to a gas.
• Example- dry ice, shrinking of ice cubes in the
  freezer overtime
• Is an endothermic change

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Deposition

• Water vapor changing directly into a solid
• Ex. Frost on a window on a cold winter night

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Temperature Change Versus Phase Change

• Temperature of a substance is a measure of the
  speed of the particles.
• Temperature of a substance changes so does the
  speed of the particles
• While a substance is undergoing a phase change
  the temperature does not change until the phase
  change is complete