Question

Explain why the number of defects in a solid increases as it is heated.

Answer 1

When a solid is heated, the motion of the atoms increases rising the level of disorder in the solid crystal structure. Bond length also increases with temperature. It may so happen that the bond length around an atom collectively increases enough to fit another atom in that space. If no atom fills that space, then there is a vacancy defect of a simple kind.

The number of defects with temperature follows a dependence like the Arrhenius equation.

[D] = exp(-E/kT)

where,

[D} is the defect concentration

k: Boltzmann Constant

E: activation energy for defect formation

T: Temperature

From the relation too, we can see the defects increase with increasing temperature.