Matter will expand or contract as a result of temperature change. 


Other Demos of Interest:

Work by Expanding Air

Objects Expanding in Vacuum

Atoms in Solids & Liquids

Possible Incorporated Topics:

  • atomic motion 
  • temperature change
  • kinetic energy
  • material properties


Matter will expand or contract as a result of a change in temperature. It can change in length, area, and volume.

Each material has a thermal expansion coefficient, which determines to what degree a material will expand/contract when undergoing a temperature change. 

Materials tend to expand when heated and contract when cooled. This is a result of the motion of the molecules in the material. When a material is heated, energy is added to the system which increases the kinetic energy of the molecules. This causes the molecules to move faster, and as a result, they become more spread apart. This accounts for the expansion that we see. 

When a material is cooled, the system loses kinetic energy so the velocity of the molecules decreases. This causes them to become more closely spaced, so overall the material contracts.


  • metal ball and loop
  • liquid nitrogen (as well as appropriate safety equipment for handling: safety glasses and cryogenic gloves)


  • note how at room temperature, the ball fits easily through the ring
  • immerse the ring in liquid nitrogen to cool it
  • note how the ball no longer fits through the ring as the diameter of the ring has contracted 

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