8. Summary and Vocabulary

Summary:

  • Evaporation is the process in which a liquid changes to a gas without becoming hot enough to boil. It occurs only at the exposed surface of a liquid.
  • Many factors affect how quickly a liquid evaporates, including the temperature of the liquid and air movement.
  • When particles evaporate from the surface of a liquid, the remaining liquid is cooler because it has less energy. This is called evaporative cooling.
  • Vaporization is the process in which a liquid boils and changes to a gas.
  • Vaporization is easily confused with evaporation, but evaporation doesn’t involve boiling.
  • The temperature at which a liquid boils and starts changing to a gas is called its boiling point. The boiling point of pure water is 100°C.
  • The process in which water vapor or any other gas changes to a liquid is called condensation.
  • The temperature at which condensation of water vapor occurs is called the dew point. The dew point varies depending on air temperature and moisture content.
  • Freezing is the process in which a liquid changes to a solid. It occurs when a liquid cools to a point at which its particles no longer have enough energy to overcome the force of attraction between them.
  • The freezing point of a substance is the temperature at which it freezes. The freezing point of pure water is 0°C.
  • Melting occurs when particles of a solid absorb enough energy to partly overcome the force of attraction holding them together. This allows them to move out of their fixed positions and slip over one another, forming a liquid.
  • The temperature at which a substance melts is called its melting point. The melting point of ice is 0°C.
  • Sublimation is the process in which a solid changes directly to a gas without going through the liquid state. Solid carbon dioxide is an example of a substance that undergoes sublimation.
  • Snow and ice undergo sublimation under certain conditions. This is most likely to happen where there is intense sunlight, very cold temperatures, and dry winds.

Vocabulary:

  • evaporation: Process in which a liquid changes to a gas without boiling.
  • vaporization: Process in which a liquid boils and changes to a gas.
  • condensation: Process in which a gas changes to a liquid.
  • freezing: Process in which a liquid changes to a solid.
  • melting: Process in which a solid changes to a liquid.
  • sublimation: Process in which a solid changes directly to a gas without going through the liquid state.

 CK-12 Foundation, Physical Science. http://creativecommons.org/licenses/by-nc-sa/3.0/