Many radioactive atoms that have large masses undergo radioactive decay by releasing a particle that is identical to a helium-4 nucleus
what changes in the original atom are expected as a result of this natural phenomenon

The atom goes through radioactive decay. It a random phenomenon and cannot be predicted. There are several types of decay, depending on the particles that the atom emits. Alpha decay happens when the nucleus ejects an alpha particle, in contrast, beta decay happens when the nucleus ejects an electron, positron and a neutrino. 

answer : one can design an experiment using a liquid and an additive that can be added to the liquid and observe the chemical changes in the reaction species.

one would need a beaker which is filled with a known amount of the liquid in which thermometer is placed to measure the temperature changes; after addition of the additive to the liquid solution one can note down the temperature change and find whether the reaction is endothermic or exothermic in nature. by subtracting the initial temperature value with the final temperature one can find the temperature changes.

various combinations of liquid and additive can be used. liquid in this case can be a known quantity of water and additives can be epsom salt or without epsom salt the experiment can be conducted to notice the changes. water and ice, hydrogen peroxide and dry yeast, vinegar and baking soda,etc.