Thermochemistry involves a study of heat and energy-related to various physical transformations and chemical reactions. A reaction may absorb or release energy and phase change may include the same namely boiling and melting. Thermochemistry is mainly concerned with a change in energy mainly regarding an exchange of energy of a system with its surroundings.


Regarding the determination of entropy, it is used to detect whether a reaction is favourable or unfavourable, spontaneous or non-spontaneous. It is likewise used in determining product and reactant quantities through a complete reaction.

Subject consolidate the theory of thermodynamics along with the theory of energy in the form of chemical bonds. It includes calculations of quantities such as free energy, enthalpy, entropy, heat capacity and combustion of heat.


Calorimetry is a science of mapping changes in state variables of a body for the reason of deriving heat transfer, related to the changes in is state due to physical changes, chemical reactions, and other undefined constraints. It is performed using a calorimeter.

Indirect Calorimeter determines heat that is produced by living creatures by measuring the production of nitrogen waste and carbon dioxide or from the amount of oxygen consumed. Direct Calorimeter can also be used to determine heat that is produced by living organisms.

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Definition of thermodynamics is useful in thermochemistry. A system is a part of a universe that can be studied. The system is surrounded by an environment. They are three types of systems that can be considered.

Also read:

  • Bomb Calorimeter
  • Open System:

    It is a system wherein the exchange of energy and matter takes place with the environment. Example: A vessel of hot water.

  • Closed System:

    It is a system which can exchange only energy and not matter. For example A balloon.

  • Isolated System:

    It is a system which cannot exchange matter nor energy with the environment. Example: an insulated bomb calorimeter. An isolated system is either a physical system or a thermodynamic system.

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