System: Any specific part of universe that is of interest to us.
Surroundings: The universe outside the system is surroundings.
Open system: System that can exchange mass and energy with its surroundings.
Closed system: System that can exchange energy but not mass with its surroundings.
Isolated system: No transfer of either mass or energy.
Exothermic process: Any process that gives of heat.
Endothermic process: Process in which heat has to be supplied to the system by the surroundings.
Internal energy: Energy of a substance due to its molecular structure and motion.
External energy: Energy of a substance due to its position or motion.
Enthalpy: Heat released or absorbed in a constant pressure process is called enthalpy.
Specific heat: Amount of heat required to raise the temperature of one gram of substance by one degree Celsius.
Heat of solution: Heat generated or absorbed when a certain amount of solute dissolves in a certain amount of solvent.
Spontaneous reactions: A reaction that does occurs under given set of conditions (e.g. at given temperature, pressure and concentration).
1st law of thermodynamics: Energy can be converted from one form to another, but cannot be created or destroyed.
2nd law of thermodynamics: The entropy of the universe increases in a spontaneous process and remains unchanged in an equilibrium process.
3rd law of thermodynamics: The entropy of a perfect crystalline substance is zero at the absolute zero temperature.
Hess’s law: When reactants are converted to products, the change in enthalpy is same whether the reaction takes place in one step or in a series of steps.
Law of conservation of energy: The total energy in the universe is constant.