Which of the following would not necessarily indicate a chemical reaction?
change in temperature
chemical precipitation of a solid
production of a gas
change in volume

Option (d) is the correct answer.

Explanation:

A change that does not cause any difference in chemical composition of a substance are known as physical change.

For example, shape, size, mass, volume, density, etc of a substance are all physical changes.

And, a change that causes changes in chemical composition of a substance is known as chemical change.

For example, precipitation, reactivity, toxicity etc are chemical change.

Therefore, change in temperature, chemical precipitation of a solid , production of a gas are all indications of a chemical change.

Thus, we can conclude that change in volume  would not necessarily indicate a chemical reaction.

water is used to store them because it would keep the radiation from getting out in the open and causing harm to the workers