Question

What is the study of the changes in the energy that accompanies chemical reactions and physical changes?

Answer 1

We study the changes in the energy that accompanies various chemical and physical changes in chemistry under the topic of thermodynamics. The thermodynamics have various branches like statistical, chemical, equilibrium, and classical thermodynamics. Several subsets of thermodynamics include thermochemistry, zeroth law, first law etc.

Complete answer:
Thermodynamics deals with the study of heat, work, and temperature and their relationship with the energy, radiation, and physical properties of matter. Thermodynamics have a subtopic called thermochemistry which deals with the study of energy changes that occur during chemical reactions and changes.
The energy stored in the chemical bonds of a substance is called chemical potential energy. When the changes occur there is a certain amount of kinetic and a certain amount of potential energy. The changes in them are studied under thermochemistry.
Hence, the study of the changes in the energy that accompanies chemical reactions and physical changes is called thermochemistry.

Note:
During physical and chemical changes, certain energy is lost, actually that lost part of energy is converted into study of the changes in the energy that accompanies chemical reactions and physical changes forms like light, sound and vibration etc. which are quite difficult to measure. The difference is small and hence this all follows the law of energy conservation.