What is a change in composition or structure called?

The correct answer to this question is Transformation. It is also known as energy conversion. It is when energy changes from one form to another. Every second that passes, an energy transformation occurs. There are many examples of energy transformations, which include chemical, mechanical, and thermal. Every morning, I make waffles I am experiencing an energy transformation.

I make them in the toaster, and for the waffles to cook, electrical energy from the socket changes into thermal energy to cook the waffles. Other examples include a blender transforming electrical energy into mechanical energy and sun changing nuclear energy into electromagnetic energy.