In thermodynamics, a measure of the heat content of a chemical or physical system
H = E + P V.
The enthalpy of a system is its actual °energy (termed the internal energy) plus the product of its volume and the external pressure Though sometimes termed "heat content,'' the enthalpy in fact includes energy not contained in the system Enthalpy proves convenient for describing processes in gases and liquids in laboratory environments, if one does not wish to account explicitly for energy stored in the atmosphere by work done when a system expands It is of little use, however, in describing processes in °nanomechanical systems, where work can take many forms: internal energy is then more convenient Enthalpy is to energy what the °Gibbs free energy is to the °Helmholtz free energy
Heat flow at constant pressure Because chemists most often conduct reactions at a constant pressure of 1 atm, enthalpy and heat of reaction are usually synonymous
Heat content or total heat, including both sensible and latent heat The amount of heat contained in a refrigerant at any given temperature with reference to -40°F
- The heat within a reaction or system The change in this is close to equal the difference between the energy needed to break bonds, and the energy gained from the new bond formations
A mathematically defined thermodynamic function of state h = u + pv where h is specific enthalpy; u is specific internal energy; p is pressure; and v is specific volume Also called heat function
A thermodynamic quantity that is the sum of the internal energy of a body and the product of its volume multiplied by the pressure: h = u + pV
also known as heat content, is the change in energy of a reaction at constant pressure Symbolized by H, the absolute enthalpy of any state is impossible to measure Instead we always measure changes in enthalpy, DH The enthalpy change for a chemical change can be calculated using Hess's law
a property of a system equal to E + PV, where E is the internal energy of the system, P is the pressure, and V is the volume of the system At constant pressure, the change in enthalpy equals the energy flow as heat
The amount of heat a substance contains determined from a predetermined base or point
A thermodynamic property of a substance defined as the sum of its internal energy plus the quantity Pv/J, where P = pressure of the substance, v = its volume, and J = the mechanical equivalent of heat H = Internal Energy + Pv/J
H (from the Greek word enthalpien, which means to heat) is a property and is defined as the sum of the internal energy U and the PV product H (from the Greek word enthalpien, which means to heat) is a property and is defined as the sum of the internal energy U and the PV product
A thermodynamic property of a substance defined as the sum of its internal energy plus the quantity Pv/J: where P = pressure of the substance, v = its volume, and J = the mechanical equivalent of heat; formerly called total heat and heat content
The sum of the internal energy plus the product of the pressure times the volume of the gas in a system: H = E + PV
Sum of the internal energy E and the product of the pressure P and volume V of a thermodynamic system (see thermodynamics). So, enthalpy H = E + PV. Its value is determined by the temperature, pressure, and composition of the system at any given time. According to the law of conservation of energy (see conservation law), the change in internal energy is equal to the heat transferred to the system minus the work done by the system. If the only work done is a change of volume at constant pressure, the enthalpy change is exactly equal to the heat transferred to the system
(thermodynamics) a thermodynamic quantity equal to the internal energy of a system plus the product of its volume and pressure; "enthalpy is the amount of energy in a system capable of doing mechanical work"
a property of a system equal to E + PV, where E is the internal energy of the system, P is the pressure of the system, and V is the volume of the system At constant pressure, where only PV work is allowed, the change in enthalpy equals the energy flow as heat (9 2)
The sum of the internal energy plus the product of the pressure times the volume of the gas ina a system
A thermodynamic property of a gas, representing the internal energy plus the P V work associated with its temperature and pressure Enthalpy is not directly measurable, but enthalpy differences are
A quantity with units of energy symbolized H and defined by H = E + PV, where E is internal energy, P is pressure, and V is volume Enthalpy is useful because at constant pressure it measures the quantity of heat that flows into or out of a system, hence differences in enthalpy can be measured directly by calorimetry The difference in enthalpy between a compound and the elements of which it is composed is called the enthalpy of formation
the amount of energy in joules required to heat 1 gram of fabric from a temperature of 20°C to its melting point