How are changes in matter realted to changes in energey?

Answer 1

Directly, as they are ways of describing the same 'thing', which we don't yet understand.

We designate matter as 'mass' (m), and energy E, with the relation mass = energy divided by the speed of light squared, or m=E /c^2

For 'Energy', this is the famous Einstein Equation; E=mc^2, which is an oversimplified version because there are two versions of mass, inertial and 'rest' mass. The above equivalent equations (under the rules of mathematics) use different versions of mass, one of a number of indications of the underlying incompletion of the special theory of Relativity often forgotten (or even denied!)

"For the time being, we have to admit that we do not possess any general theoretical basis for physics, which can be regarded as its logical foundation." A.Einstein 1940.