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is to be lost in
the service of others.

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Heat Energy

The sun does not shine for a few trees and flowers, but for the wide world's joy.

Henry Ward Beecher

HEAT

  • Thermal energy
  • The energy of moving molecules
  • States (phases) of matter
    • Solids
    • Liquids
    • Gases
    • Phase changes

  • The kinetic theory of matter:
    • atoms and molecules (particles) are in constant motion
    • the higher the temperature - the higher the speed
      • increased heat energy make atoms and molecules move faster
  • Gases have:
    • more kinetic energy - higher temperatures - more heat
    • particles that move quickly and randomly
    • no fixed shape or volume
  • Liquids have:
    • less kinetic energy - lower temperatures - less heat
    • particles move quickly
    • a fixed volume, but take the shape of containers
  • Solids have:
    • the least kinetic energy - lowest temperatures - less heat
    • particles vibrate in place
    a fixed volume and shape

 

  • Phase changes (changes of state) require a gain or loss of energy to occur.
    • gas to liquid
      • condensation
      • energy loss
      • endothermic
    • liquid to solid
      • freezing
      • energy loss
      • endothermic
    • solid to liquid
      • melting
      • energy gain
      • exothermic
    • liquid to gas
      • evaporation
      • energy gain
      • exothermic
    • gas to solid
      • crystalization (snowflakes)
      • energy loss
      • endothermic
    • solid to gas
      • sublimation
      • energy gain
      • exothermic

 

  • The transfer of thermal energy between objects is called heat

 

  • Thermal energy (heat energy) moves from one place to another because of the difference in temperature between them. The energy transfer is always from hot to cold.

 

  • Heat can be transferred (moved) three ways:

    Conduction

      • The movement of heat from one molecule to another
      • Needs direct contact
      • Heat flows from a higher-temperature area to a lower-temperature one

Convection

      • The movement heat by currents in liquids or gases
      • circulation through a fluid
      • cool air sinks down, while warmer air rises to the top

Radiation

      • Energy movement through electromagnetic waves
      • A way in which energy is transferred from place to place in the form of a wave

 

 

Original Graphics Sources:

http://itl.chem.ufl.edu/2045_s99/lectures/lec_f.html

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