In: Physics
Weight of the cube is 
Volume of cube 
Mass of the cube 
Using ideal gas equation, 

  
  
Weight of the cube is 
Pressure 
  
Temperature 
Molar mass of air 

Mass of cube is 
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If the air is cooled to 
Pressure 
Using ideal gas equation, 
, Pressure is constant , so 
As the temperature decreases at constant pressure, Volume of the cube decreases.
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