Which is one way to determine whether a reaction was a chemical reaction or a nuclear reaction?

check for a change in total mass during the reaction.

check to see if any energy was released during the reaction.

measure the temperature change during the reaction.

measure the total volume of gas released during the reaction.

check for a change in total mass during a reaction.

According to the law of conservation of mass during a chemical change the total mass of the products remains equal to the total mass of the reactants: there is not change in the total mass.

During nuclear reactions the mass can change due to the huge release of energy which proceeds from mass change, as per the famous equation ΔE =Δm. c^2.