MCAT Content / Energy Changes In Chemical Reactions / First Law Of Thermodynamics Conservation Of Energy In Thermodynamic Processes

First Law of Thermodynamics: Conservation of Energy in Thermodynamic Processes

Topic: Energy Changes In Chemical Reactions

The first law of thermodynamics states that the internal energy of an isolated system is constant. While the energy in the system may undergo a series of changes when it is restored to its initial state, the same energy value will be found.

The first law of thermodynamics has been commonly defined as the inability to create or destroy matter. To put this law into the perspective of systems and states, energy cannot be added or taken from a system but can be transferred or converted into forms like heat or work.

The first law of thermodynamics can be represented by the following equation:

ΔU = q + w

Where ΔU represents the internal energyq represents heat exchange, and w represents work exchange.


Key Points

• The first law of thermodynamics states that the internal energy of an isolated system is constant.

• While the energy of a system cannot be subtracted from or added to, the energy can be converted into different forms such as heat or work.


Key Terms

heat: transfer of energy that results in the change of temperature

work: transfer of energy that can result in the change of pressure and volume

internal energy: the energy contained within the system



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