Energy exists in many forms, such as heat, light, chemical energy, and electrical energy. Energy is the ability to bring about change or to do work. Thermodynamics is the study of energy.

The thermodynamics is concerned with energy changes accompanying a given process (physical or chemical) and not with the total energy of the body. The various forms of energy are kinetic energy, potential energy, electrical energy, radiant energy, mass-energy, nuclear energy, and chemical energy.

## What is Thermodynamics?

The study of thermodynamics is based on three generalizations, called the first, second and third law of thermodynamics. All these laws are based on human experience and although there is no formal proof for these laws, nothing contrary to these laws has been found so far and nothing contrary is expected.

### First Law of Thermodynamics

The total amount of energy and matter in the Universe remains constant, merely changing from one form to another.

The First Law of Thermodynamics (Conservation) states that energy is always conserved; it cannot be created or destroyed. In essence, energy can be converted from one form into another

### The Second Law of Thermodynamics

It states that “in all energy exchanges if no energy enters or leaves the system, the potential energy of the state will always be less than that of the initial state.”

This is also commonly referred to as entropy. A watch spring-driven watch will run until the potential energy in the spring is converted, and not again until energy is reapplied to the spring to rewind it. A car that has run out of gas will not run again until you walk 10 miles to a gas station and refuel the car.

Once the potential energy locked in carbohydrates is converted into kinetic energy (energy in use or motion), the organism will get no more until energy is input again. In the process of energy transfer, some energy will dissipate as heat.

Entropy is a measure of disorder: cells are NOT disordered and so have low entropy. The flow of energy maintains order and life. Entropy wins when organisms cease to take in energy and die.

### Potential vs. Kinetic energy

• Potential energy, as the name implies, is the energy that has not yet been used, thus the term potential.
• Kinetic energy is energy in use (or motion). A tank of gasoline has a certain potential energy that is converted into kinetic energy by the engine.

When the potential is used up, you’re outta gas! Batteries, when new or recharged, have a certain potential.

When placed into a tape recorder and played at loud volume (the only settings for such things), the potential in the batteries is transformed into kinetic energy to drive the speakers.

When the potential energy is all used up, the batteries are dead. In the case of rechargeable batteries, their potential is re-elevated or restored.

In the hydrologic cycle, the sun is the ultimate source of energy, evaporating water (in a fashion raising its potential above water in the ocean).

When the water falls as rain (or snow) it begins to run downhill toward sea-level. As the water gets closer to sea-level, its potential energy is decreased.

Without the sun, the water would eventually still reach sea-level, but never be evaporated to recharge the cycle.

Chemicals may also be considered from potential energy or kinetic energy standpoint. One pound of sugar has a certain potential energy.

If that pound of sugar is burned the energy is released all at once. The energy released is kinetic energy (heat).

So much is released that organisms would burn up if all the energy was released at once. Organisms must release the energy a little bit at a time.

Energy is defined as the ability to do work. Cells convert potential energy, usually in the form of C-C covalent bonds of ATP molecules, into kinetic energy to accomplish cell division, growth, biosynthesis, and active transport, among other things.

## What are the limitations?

There are a few limitations.

1. The laws of thermodynamics are applicable only matter in bulk, ie, assembling of a large number of molecules (macroscopic system), and not to individual molecules of atoms.
2. It predicts about the feasibility, direction, and extent of a given process under a given set of conditions, it does not tell anything about the rate at which a given process may proceed, ie, it provides o information regarding the time taken to reach equilibrium.
3. It concerns itself only with the initial and final states of a system and gives no information about the path taken (a mechanism) by a process.

Source: Wikipedia