These traits describe either a chemical or a nuclear reaction. which statements describe a nuclear reaction? check all that apply. involves the loss, gain, or sharing of electrons may involve a change in total mass involve relatively low energy changes occur outside the nucleus involve very high-energy changes involve changes in nuclides when decay occurs

The statements that describe a nuclear reaction are may involve a change in total mass, involve very high-energy changes, and involve changes in nuclides when decay takes place.  

There are two kinds of nuclear reactions, that is, fission and fusion. Fusion involves the fusion of two light atoms into a heavier atom, while fission involves the splitting of an unstable isotope (with a high mass number) into stable elements of lower mass number, which vary in features from the parent atoms. Both the reactions discharge huge concentration of energies in the process.  

it can be observed without changing the identity of the object.

it depends on what substance you're talking about as well as many other factors. in quantum mechanics, the observation of particles affects the observers ability to measure certain properties. for example: you can know the velocity of a particle, but you can't know it's position; or you can know it's position, but not it's velocity. it's like trying to find out where a grain of sand is by throwing other grains of sand at it. once you find out where it is, it's been moved. it's also like trying to find an answer to the question of whether or not a tree falling in a forest makes a sound if nobody is there to hear it. paradoxically, the only way to find out is to be there and hear it.