Some terminologies:

System: system is a set of interacting or interdependent components forming an integrated whole or a set of elements (often called ‘components’ ) and relationships which are different from relationships of the set or its elements to other elements or sets.

Surroundings In thermodynamics, the term (and its synonym, environment) is used in a more restricted sense, meaning everything outside the thermodynamic system. Often, the simplifying assumptions are that energy and matter may move freely within the surroundings, and that the surroundings have a uniform composition.

Universe; the system and surrounding together constitute the universe.

Boundary: the system is separable from the surrounding by a boundary which may be real or imaginary.

Homogenous system: the system is completely uniform throughout

Heterogeneous system: the system is not uniform throughout.

Open system: An open system is a system which continuously interacts with its environment. The interaction can take the form of information, energy, or material transfers into or out of the system boundary, depending on the discipline which defines the concept.

Closed system; In thermodynamics, a closed system can exchange energy (as heat or work), but not matter, with its surroundings. In contrast, an isolated system cannot exchange any of heat, work, or matter with the surroundings, while an open system can exchange all of heat, work and matter.

Enthalpy: Enthalpy is a measure of the total energy of a thermodynamic system. It includes the internal energy, which is the energy required to create a system, and the amount of energy required to make room for it by displacing its environment and establishing its volume and pressure.

Entropy: a quantitative measure of the amount of thermal energy not available to do work. It is a measure of the disorder or randomness in a closed system.

Entropy=unavailable energy/temperature

Endothermic: describes a process or reaction in which the system absorbs energy from the surroundings in the form of heat.

Exothermic : describes a process or reaction that releases energy from the system,

Exergonic: “releasing energy in the form of work”.

Endergonic: “absorbing energy in the form of work.”

Gibbs free energy : The amount of energy which is capable of doing work during a reaction at constant temperature and pressure is called Gibbs free energy.

Value of ΔG = -ve ( Exothermic)

Value of ΔG = +ve ( Endothermic)