G a hot plate is used to transfer 400 cal of heat to a breaker. how much ice melts in thsi process

It is a mixture. simply put, a compound must be pure, that is, of only one chemical structure and composition. a mixture is made of different chemical substances (i.e. elements, molecules, compounds) that are not chemically bonded to each other, but instead physically grouped together, as in the case of gasoline (a homogeneous solution).

Answeropposite;

Ithink about 50 % of an original isotope's number of atoms remain

Elements would be the right answer