Third law of thermodynamics facts for kids

The third law of thermodynamics says:

• If an object reaches the absolute zero of temperature (0 K = −273.15C = −459.67 °F), its atoms will stop moving.

The definition is: at absolute zero , the entropy of a perfectly crystalline substance is zero.

Experimentally, it is not possible to obtain −273.15°C, as of now. It is found that most of the gases either liquify or solidify before reaching such a temperature, gaseous molecules no longer remaining. So far, scientists have been able to get close to, but not exactly, absolute zero. This may change in the future.

Related pages

• Zeroth law of thermodynamics
• First law of thermodynamics
• Second law of thermodynamics

Images for kids

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  a) Single possible configuration for a system at absolute zero, i.e., only one microstate is accessible. Thus S = k ln W = 0. b) At temperatures greater than absolute zero, multiple microstates are accessible due to atomic vibration (exaggerated in the figure). Since the number of accessible microstates is greater than 1, S = k ln W > 0.

• 

  Fig. 1 Left side: Absolute zero can be reached in a finite number of steps if S(0,X1)≠S(0, X2). Right: An infinite number of steps is needed since S(0,X1)= S(0,X2).

See also

In Spanish: Tercer principio de la termodinámica para niños