Thermochemistry, Internal Energy, and Work

Vocabulary practice flashcards covering fundamental concepts of thermochemistry, internal energy, work, enthalpy, and state functions.

Energy

The ability to do work or to transfer heat.

Joule ($\text{J}$)

The primary unit of energy, equivalent to kilograms times meters squared divided by seconds squared ($\text{kg}\cdot\text{m}^2/\text{s}^2$).

First Law of Thermodynamics

The fundamental principle stating that energy can be converted from one form to another, but it cannot be created or destroyed.

System

The specific part of the universe being studied that performs work, has work done on it, or gains and loses heat.

Surroundings

Everything else in the universe located outside the defined system.

Internal Energy ($E$)

The sum of all kinetic and potential energies of all components in a system.

Change in Internal Energy ($\Delta E$)

The difference between the final and initial internal energy ($\Delta E = E_{\text{final}} - E_{\text{initial}}$), which can also be calculated as the sum of heat and work ($\Delta E = q + w$).

Endothermic Process

A thermodynamic process in which heat is absorbed by the system from the surroundings, resulting in a positive value for heat ($q > 0$).

Exothermic Process

A thermodynamic process in which heat is released by the system into the surroundings, resulting in a negative value for heat ($q < 0$).

State Function

A property that depends only on the present initial and final states of the system, completely independent of the specific path taken between them.

Enthalpy ($H$)

A state function defined as the internal energy of the system plus the product of its pressure and volume ($H = E + PV$).

Pressure-Volume Work ($w$)

The work resulting from a change in volume against an external pressure, calculated at constant pressure as $w = -P\Delta V$.

Chemical Bond Formation

An energetically favorable process that releases energy from the system into the surroundings when bonds are created.

Chemical Bond Breaking

A process that consumes energy, requiring an input of energy into the system to break chemical bonds apart.

Liter-Atmosphere ($\text{L}\cdot\text{atm}$)

A unit of work and energy derived from pressure and volume changes, where $1\,\text{L}\cdot\text{atm} = 101.3\,\text{J}$.