Question

Name an oxide that is yellow when hot and white when cold.

Answer 1

An oxide that is yellow when hot and white when cold is :

Zinc oxide ($\mathrm{ZnO}$) :

• Zinc oxide is an amphoteric oxide that forms zinc salt when it combines with acids.
• When zinc oxide combines with a strong base to generate zincates, it takes on a yellow tint that fades when it cools.
• Zinc oxide is a white powder that is water insoluble.
• In the form of zincate, it can be found in the earth's crust.
• As a result, zinc oxide is manufactured commercially.
• Zinc ore - zincate is yellow in colour due to the presence of magnesium and other impurities.
• When heated, crystalline zinc oxide changes colour in a reversible manner; this phenomenon is known as thermochronic.
• When heated, it changes colour from white to yellow, then returns to white when cooled.