thermochemistry

the study of the relationship between chemistry and energy

energy

the capacity to do work

work

the result of force acting through a distance

heat

the flow of energy caused by a temperature difference

kinetic energy

the energy associated with motion of an object

thermal energy

a type of kinetic energy associated with the temperature of an object, arising from the motion of individual atoms or molecules in the object; see also heat

potential energy

the energy associated with the position or composition of an object

chemical energy

the energy associated with the relative positions of electrons and nuclei in atoms and molecules

law of conservation of energy

energy can neither be created nor destroyed, only converted from one form to another

system

in thermodynamics, the portion of the universe that is singled out for investigation

surroundings

in thermodynamics, everything in the universe that exists outside the system under investigation

thermodynamics

the general study of energy and interconversions

first law of thermodynamics

the total energy of the universe is constant

internal energy (E)

the sum of the kinetic and potential energies of the of the particles that compose the system

state function

a function whose value depends only on the state of the system, not on how the system got to that state

thermal equilibrium

the point at which there is no additional net transfer of heat between a system and its surroundings

heat capacity (C)

the quantity of heat required to change a systems temperature by 1 degree Celsius

specific heat capacity

the amount of heat required to raise the temperature of 1 gram of a substance by 1 degree Celsius

molar heat capacity

the amount of heat required to raise the temperature of 1 mole of a substance by 1 degree Celsius

pressure - volume work

the work that occurs when a volume change takes place against an external pressure

calorimetry

the experimental procedure used to measure the heat evolved in a chemical reaction

enthalpy (H)

the sum of the internal energy of a system and the product of its pressure and volume; the energy associated with the breaking and forming bonds in a chemical reaction (internal energy)

endothermic reaction

a chemical reaction that absorbs heat from its surrounding; for an endothermic reaction delta H >0

exothermic reaction

a chemical reaction that releases heat to its surroundings; for an exothermic reaction, delta H < 0

enthalpy (heat) of reaction

the enthalpy change for a chemical reaction

Hess’s Law

1) if a chemical equation is multiplied by some factor, then heat of reaction is also multiplied by the same factor

2) if a chemical equation is reversed, the heat of reaction changes signs

3) if a chemical equation can be expressed as the sum of a series of steps, the heat of reaction for the overall equation is the sum of the heats of reaction for each step

standard state of gas

pure gas at 1 atm

standard state of a liquid or solid

pure substance in its most stable form at 1 atm and at the temperature of interest (normally 25 degrees Celsius)

standard enthalpy change

the change in enthalpy for a process when all reactants and products are in their standard states

standard enthalpy of formation for a pure compound

the change in enthalpy when 1 mole of the compounds forms from its constituent elements in their standard states

standard enthalpy of formation for a pure element in its standard state

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