Question

what chemical change would you observe when mecury oxide is heated​

Answer 1

Answer:

When it is heated, it decomposes into mercury metal and oxygen gas. A reaction is also considered to be a decomposition reaction even when one or more of the products are still compounds

Answer 2

Answer:

The chemical change observed when mercury oxide is heated is that it decomposes into mercury metal and oxygen gas.

Explanation:

Mercury oxide is a red solid compound. The oxidation state of mercury in mercury oxide is +2. When mercury oxide is heated, it easily decomposes into mercury metal and oxygen gas. The red coloured mercury oxide becomes silver due to the formation of mercury metal. The oxygen gas is evolved along with it.  

This is considered a chemical change because the reaction is accompanied by a change in colour and the evolution of a gas.