The Laws of Thermodynamics

THE LAWS OF THERMODYNAMICS

by Antonio C. Antonio

January 6, 2015

In environmental science, it is inevitable not to talk about the energy flow in an ecosystem.  The primary source of energy in the biosphere is the sun.  The energy that the sun provides is in the form of radiation; usually light and thermal or heat energy.  Light triggers photosynthesis while heat energy causes movement of molecules.  Energy flows are lost in the process but not before it performs work in the ecosystem such as in the metabolism of living organisms and their growth and reproduction.  While some energy is expended, some energy, on the other hand, gets stored.  The expenditure and storage of energy are governed by the Laws of Thermodynamics.

Thermodynamics is the branch of physical science that deals with the relations between heat and other forms of energy (therefore: mechanical, electrical or chemical energy) and, by extension, of the relationships between all forms of energy.  The Four Laws of Thermodynamics define fundamental physical quantities (therefore: temperature, energy and entropy) that characterize thermodynamic systems.  The laws describe how these quantities behave under various circumstances and forbid certain phenomena (such as perpetual motion).

The Four Laws of Thermodynamics are:

ZEROTH LAW OF THERMODYNAMICS – If two systems are in thermal equilibrium respectively with a third system, they must be in thermal equilibrium with each other.  This law helps define the notion of temperature.

FIRST LAW OF THERMODYNAMICS – When energy passes, as work, as heat, or with matter, into or out from a system, its internal energy changes in accordance with the Law of Conservation of Energy.  Equivalently, perpetual motion machines of the first kind are impossible.

SECOND LAW OF THERMODYNAMICS – In a natural thermodynamic process, the sum of the entropies of the participating thermodynamic systems increases.  Equivalently, perpetual motion machines of the second kind are impossible.

THIRD LAW OF THERMODYNAMICS – The entropy of a system approaches a constant value as the temperature approaches absolute zero.  With the exception of gasses, the entropy of a system at absolute zero is typically close to zero and is equal to the log of the multiplicity of the quantum ground state.

The Laws of Thermodynamics are important fundamental laws in physics and they are applicable in other natural sciences.  These Laws of Thermodynamics, seemingly hard to comprehend by ordinary minds, are essential and inevitable parts in environmental science.  This is the reason why, in the broader sense of environmentalism, there is a need to create some degree of awareness on the Laws of Thermodynamics.

Just my little thoughts…

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