Thermodynamics 1 terms

Thermodynamics

a branch of physical science that treats various phenomena of energy and the related properties, especially of the laws of transformation of heat into other forms of energy and vice versa.

Temperature

an indication or degree of hotness and coldness and therefore a measure of intensity of heat

Absolute Temperature

is the temperature measured from absolute zero

Absolute Zero

temperature at which the molecules stop moving

Temperature Interval

difference between two temperature readings from the same scale, and the change in temperature through which the body is heated

Absolute pressure

True pressure measured from the level of atmospheric pressure by most pressure recording instruments like pressure gage and open ended manometer

Atmospheric pressure

Pressure obtained from barometric reading

Pgage

it is negative when the pressure is vacuum

System

it is the collection of matter under consideration enclosed within a boundary

Surrounding

the region outside the boundary or the space and matter external to a system

Closed system

a system in which there is no transfer of matter across the boundary

Open System

a system in which there is a flow of matter through the boundary

Isolated System

a system in which neither mass nor energy cross the boundaries and it is not influenced by the surroundings

Non flow proces

a process that takes place in a closed system (compressor)

Steady flow process

a process that takes place in an open system in which the quantity of matter within the system is constant. (Turbine)

Law of conservation of mass

Mass entering the system is equal to the sum of the stored mass and the mass that leaves the system

Heat

a form of energy associated with the kinetic random motion of large number of molecules

Sensible Heat

the heat needed to change the temperature of the body without changing its phase.

Latent Heat

the heat needed by the body to change its phase without changing its temperature.

Latent Heat of Fusion

Solid to liquid

Latent Heat of Vaporization

liquid to gas

Entropy

the measure of the randomness of the molecules of a substance

Enthalpy

the heat energy transferred to a substance at a constant pressure process

Internal Energy

the energy stored within the body. It is the sum of the kinetic energies of all its constituent particles plus the sum of all the potential energies of interaction among these particles

First Law of Thermodynamics

Energy cannot be created nor be destroyed, it can only be transformed from one form to another.

Second Law of Thermodynamics

Heat cannot be transferred from a cold body to a hot body without an input of work. It states also that heat cannot be converted 100 % into work.

Clausius Statement applied to heat pump

It is impossible to construct a heat pump that operated without an input of work

Kelvin Plank Statement applied to heat Engine

It is impossible to to construct a heat engine which operates in a cycle and receives a given amount of heat from a high temperature body and does an equal amount of work

Third Law of Thermodynamics

The total entropy of pure substances approaches zero as the absolute thermodynamic temperature approaches zero.