Thermodynamics and Energetics

This process proceeds without any change in enthalpy or specific enthalpy (H), e.g. throttling process.

This state of matter has relatively low density and viscosity. It also has relatively great expansion and contraction with changes in pressure and temperature. It has the highest magnitude of internal energy among the three states of matter.

In endothermic process, a system absorbs energy from the surroundings in the form of heat. During summers, heat absorbed from the surrounding is used in sweating to maintain the body temperature.

It is the energy of molecules due to vibrations of their atoms to & fro. It is associated with both kinetic & potential energy as the vibrational motion is along the bond.

Due to isothermal contraction of the refrigerator gas, heat is liberated into the surroundings, i.e. in room. So, the temperature of the room will increase.

It is defined as a measure of the total energy of a thermodynamic system including the internal energy. It is a state function and an extensive property of the system.

This process is an idealized model of a thermodynamic process, which takes place infinitely slowly. Practically no real process is quasistatic.

All are state functions.

This system exchange both matter and energy with the surroundings. Since plant exchanges both matter and energy with the surroundings, photosynthesis is an example of open system.

The kinetic energy is made up of different types of movements of particles. As the number of the movements are not same, K.E. has fluctuating value & not absolute value. The thermodynamic state function; like E, H, T, etc. depends on kinetic energy. Hence they have no absolute value.

A spark is produced at the TDC by spark plug, which ignites the compressed air-fuel mixture. This creates an explosion in the combustion chamber. This force gushes the piston towards BDC.

The negentropy of a living system is the entropy, which consigns to keep its own entropy low. It lies at the junction of entropy and life.

Erwin Schrodinger was a theoretical biologist. He coined the term negative entropy in thermodynamics.

It tells us about how much of the initial matter was contained in the system and how much will be left after the process is complete. It is an extensive property.

This entropy is associated with the physical set up of a polymer chains that allines a compact or globular state in solution. This concept is most commonly applied to biological macromolecules such as proteins and RNA.

The enthalpy of all the elememts in standard physical state is always zero.

In an endothermic change, energy is absorbed. Heat has to be absorbed in fusion of ice to give water.

Change in enthalpy does not depen upon path followed in a reaction. It only depends upon initial & final state of the reaction. So, it is a state function.

During adiabatic expansion, there is increase in volume without heat flow, in or out. Inside a refrigerator, due to the isolated system, the adiabatic expansion of refrigerator gases like freon takes place by using the heat from the gas itself. This causes lowering of temperature of the gas, i.e. cooling effect of the refrigerator.

The diesel cycle is an illuminated cycle for compressing the ignition engines (ones that don't use a spark plug).

In this process, no heat is exchanged into or out of a system so, dQ=0. We can control heat flow either by surrounding the system with thermally insulating material or by carrying out the process so promptly that there is not enough time for ascertainable heat flow.

In adiabatic process, the net heat transfer is zero. The heat content of the system is used for the expansion of the gas, which causes a decrease in the temperature of the system.

Hess's Law states that the heat evolved or absorbed in a chemical process is the same whether the process takes place in one or in several steps.

The molecules of gases do not exert any force of attraction or repulsion on each other, except at the time of collision. Thus, the molecules do not have any potential energy. Their energy is only kinetic energy.

Enthalpy is a thermodynamic function of a system. It is equivalent to the sum of the internal energy of the system plus the product of its volume multiplied by the pressure exerted on it by its surroundings. Since heat is absorbed from the surroundings therefore the enthalpy of the ideal gas increases.