Che 131 Lect-18: Calorimetry and Energy Changes Flashcards

Vocabulary practice flashcards covering core thermodynamics concepts, state functions, work, enthalpy, heat capacities, heating curves, and calorimetry from Stony Brook University Che 131 Lecture 18.

Potential Energy

The energy an object possesses by virtue of its position, which can be converted into other forms of energy.

Electrostatic Energy ($E_{\text{el}}$)

Potential energy at the molecular level caused by electrostatic interactions, proportional to $\frac{Q_1 \times Q_2}{d}$, where $Q_1$ and $Q_2$ are charges separated by distance $d$.

System

The specific part of the universe that is selected for thermodynamic study.

Surroundings

The rest of the universe outside of the thermodynamic system being studied.

Isolated System

A system that cannot exchange either energy or matter with its surroundings, such as a thermos bottle containing hot soup with a tightly screwed lid.

Closed System

A system that can exchange energy but cannot exchange matter with its surroundings, such as a cup of hot soup covered with a lid.

Open System

A system that can exchange both energy and matter with its surroundings, such as an open cup of hot soup releasing steam.

State Function

A thermodynamic quantity whose value depends only on the present equilibrium state of the system (e.g., temperature, pressure, volume) and is independent of the path or history taken to reach that state.

First Law of Thermodynamics Equation

$\Delta E = q + w$, where $\Delta E$ is the change in internal energy of the system, $q$ is the heat added to or absorbed by the system, and $w$ is the work done on or by the system.

Pressure-Volume Work ($P\text{-}V$ Work)

Work associated with the expansion or compression of a gas system against external pressure, represented by $w = -P\Delta V$.

Exothermic Process

A process in which heat flows from the system into its surroundings, characterized by $q < 0$ and $\Delta H < 0$.

Endothermic Process

A process in which heat flows into the system from its surroundings, characterized by $q > 0$ and $\Delta H > 0$.

Enthalpy ($H$)

A state function defined as $H = E + PV$, where the change in enthalpy at constant pressure equals the heat flow ($\Delta H = q_P = \Delta E + P\Delta V$).

Bomb Calorimeter

A constant-volume device used to measure the heat released during a combustion reaction, where $\Delta H = -q_{\text{cal}} = -C_{\text{cal}}\Delta T$.

Molar Heat Capacity ($c_p$)

The heat required to raise the temperature of $1\,\text{mole}$ of a substance by $1\,^{\circ}\text{C}$ at constant pressure, calculated using $q = n c_p \Delta T$.

Specific Heat ($c_s$)

The heat required to raise the temperature of $1\,\text{gram}$ of a substance by $1\,^{\circ}\text{C}$ at constant pressure, calculated using $q = m c_s \Delta T$.

Heat Capacity ($C_p$)

The total quantity of heat needed to raise the temperature of a specific object or system by $1\,^{\circ}\text{C}$ at constant pressure.

Molar Heat of Fusion ($\Delta H_{\text{fus}}$)

The heat needed to convert $1\,\text{mole}$ of a solid at its melting point into $1\,\text{mole}$ of liquid, calculated using $q = n\Delta H_{\text{fus}}$.

Molar Heat of Vaporization ($\Delta H_{\text{vap}}$)

The heat needed to convert $1\,\text{mole}$ of a liquid at its boiling point into $1\,\text{mole}$ of vapor, calculated using $q = n\Delta H_{\text{vap}}$.

Heating Curve Phase Change Region

A flat, horizontal portion of a temperature-versus-heat plot where heat addition drives a phase transition at constant temperature ($\Delta T = 0$), evaluated using $q = n\Delta H$.

Thermal Equilibrium

The condition reached when materials of different temperatures in thermal contact exchange heat until they reach the exact same temperature ($q_1 + q_2 = 0$).