Why does `ZnO` show increased electrical conductivity and turns yellow on heating?

Explanation

On heating, `ZnO` loses `O_(2)` follows:
`ZnO overset(Delta)rarr Zn^(2+) + (1)/(2) O_(2) 2 e^(-)`
`Zn^(2+)` ions thus formed are entrapped into the interstitial sites while electrons are entrapped in the neighbouring inerstitial sites. These entrapped electrons increase the electrical conductivity of `ZnO` and become yellow. On cooling, it again turns into white solid.