Which situation is an indication that a chemical change has occurred?
a. a gas is formed.
b. no heat is released.
c. the temperature does not change.
d. no color change occurs.

Option (A) is the correct answer.

Explanation:

Chemical changes are defined as the change which tend to show difference in chemical composition of a substance.

For example, toxicity, reactivity, combustion etc are all chemical properties.

So, in the given situation formation of bubbles shows that a gas has been formed which is a chemical change.

A chemical change will always lead to the formation of a new compound and this change is irreversible in nature by any physical means.

On the other hand, a change which is unable to bring any difference in chemical composition of a substance is known as a physical change.

For example, change in shape, size, mass, volume etc are all physical properties.

Thus, we can conclude that a gas is formed is an indication that a chemical change has occurred.