Thermodynamics

Week 8 and week 9 content

Open System

A system where both energy and material can be exchanged with the surroundings.

Closed System

A system that can exchange energy but not material with its surroundings.

Isolated System

A fully sealed system that cannot exchange energy or matter with its surroundings.

The Universe (in thermodynamics)

The entire scope of the system under study and its surroundings.

First Law of Thermodynamics

Energy cannot be created or destroyed, only transformed or transferred.

Internal Energy Change Formula

$$\Delta U = q - w$$

Heat Flow ($q$)

The transfer of thermal energy into or out of a system.

Work ($w$)

Energy transferred by the system to its surroundings.

Pressure-Volume Work Formula

$$w = P \times \Delta V$$

Work during Expansion

Occurs when volume increases ($\Delta V > 0$) and work done by the system is positive.

Work during Compression

Occurs when volume decreases ($\Delta V < 0$) and work done on the system is negative.

Heat Capacity ($C$)

The amount of heat required to raise the temperature of a system by one degree Celsius.

Molar Heat Capacity ($C_m$)

Heat capacity per mole of material, units are $J\,K^{-1}\,mol^{-1}$.

Specific Heat ($c$)

Heat capacity per gram of material, units are $J\,K^{-1}\,g^{-1}$.

Extensive Quantities

Properties that scale with system size, e.g., internal energy and volume.

Intensive Quantities

Properties that do not depend on system size, e.g., temperature and pressure.

Calorimetry

The process of measuring heat changes in chemical reactions.

Enthalpy ($H$)

A state function defined as $H = U + PV$.

Endothermic Process

A process where $\Delta H > 0$, meaning heat is absorbed.

Exothermic Process

A process where $\Delta H < 0$, meaning heat is released.

Hess's Law

The total enthalpy change for a process is the sum of the changes for individual steps.

Gibbs Free Energy ($G$)

A thermodynamic potential defined as $G = H - TS$ .

Criteria for Spontaneity

A process is spontaneous if $\Delta G < 0$.

Bond Breaking

Always an endothermic process where energy must be added to break bonds.

Bond Making

Always an exothermic process where energy is released when bonds are formed.

Second Law of Thermodynamics

The total entropy of the universe must increase for any spontaneous process.