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Heat and Work are both forms of energy.

The state of a system is changed by the supply or removal of energy in the form of heat or work.

The difference between the two is that heat transfer achieves or utilizes random molecular motion. Whereas work energy transfer achieves or utilizes uniform, concerted molecular motion.

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Functions governing transition between states are called path functions.
Heat, q and Work, w.
** A state function describes the current state of a system.**

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Isothermal implies constant temperature, T.
Isobaric implies constant pressure, P.
Isochoric implies constant volume, V.
State functions,
Pressure, p
Volume, V
Mass, m
Quantity, n
Internal Energy, U
Enthalpy, H
Entropy, S
Gibbs Energy, G

# data[].attributes.body
The state of a thermodynamic system is defined by a series of state functions. Generally, the change of the state of a system is accompanied by a change in it's state functions. It is however possible for a system to change state whilst on or more of it's states functions remains unchanged.

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*A diathermic system allows heat flow into or out of the system.
*An adiabatic system prevents heat flow into or out of the system.

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*An open system may exchange both energy and matter with its surroundings.
*A closed system may exchange energy but not matter with its surroundings.
*An isolated system may exchange neither energy nor matter with its surroundings.

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*The boundary may be actual or notional.
*It controls transfer of work, heat and matter from the system to the surroundings and vice-versa.
*The boundary may or may not impose restrictions on such transfers.

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*Universe, is a sphere of radius 46.6 billion light years.
1 light year = 9.46 quadrillion meters.
So, diameter of universe is 880 Ym. 1 Ym = 1*10^24.

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The Universe is therefore the system plus its surroundin

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Thermodynamic surroundings are defined as everything other than the thermodynamic system. In other words, the entire rest of the Universe.
*Surrounding are assumed infinite and remain at constant T & P.
So, the vast size of the Universe validates this assumption.

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A thermodynamic surroundings are defined as any part of the Universe under consideration.