CHEM 1400 Study Guide

More microstates for a macrostate mean greater entropy in a system. Microstate is a specific way things are arranged; macrostate is the overall state.

In any spontaneous process, the universe's entropy increases. This means ΔSuniverse = ΔSsystem + ΔSsurroundings is positive in a spontaneous process.

ΔGsystem = ΔHsystem – TΔSsystem. Calculating ΔGsystem is easier than calculating ΔSuniverse for determining thermodynamic favorability.

Spontaneous processes occur naturally, without external intervention. They have a positive ΔSuniverse.

Gibbs free energy (ΔG) is the amount of energy available in a chemical process to do useful work at constant temperature and pressure.

Use ΔGsystem instead of ΔSuniverse to predict thermodynamic favorability because calculating ΔGsystem is easier. Positive ΔG means non-spontaneous.

ΔH: enthalpy, ΔS: entropy, and ΔG: Gibbs free energy play different roles in whether reactions occur. The signs of these properties at different temperatures determine reaction spontaneity.

The favorability (spontaneity) of a reaction can change with temperature. This depends on the signs of ΔH (enthalpy) and ΔS (entropy).

Temperature remains constant during a phase change because the added heat energy is used to overcome intermolecular forces, not to increase the average kinetic energy of the molecules.

A property of a system that depends only on the current state of the system, not on the path taken to reach that state.

A property of a system that depends on the path taken to reach the current state.

The heat absorbed or released by a system during a process at constant pressure.

A measure of the disorder or randomness in a system.

The enthalpy change for a liquid turning into a gas.

The specific arrangement of atoms and energy levels in a system.

Observable properties of a system, like temperature and pressure.

Attractive forces between molecules, influencing physical properties like boiling point and solubility. They include London dispersion forces (LDFs), dipole-dipole interactions, and hydrogen bonding.

Temporary, weak attractions between all molecules due to temporary fluctuations in electron distribution, creating temporary dipoles. Stronger with larger, more polarizable molecules.

Attractions between permanent dipoles in polar molecules, where one end is slightly positive and the other slightly negative.

A strong type of dipole-dipole interaction involving a hydrogen atom bonded to a highly electronegative atom like oxygen, nitrogen, or fluorine.

A symbolic representation of a chemical reaction, using chemical formulas to show the reactants and products, and coefficients to balance the number of atoms of each kind.

Adjusting the coefficients in front of chemical formulas to ensure the same number of atoms of each element appears on both the reactant and product sides.

A unit of amount, representing 6.022 x 10^23 (Avogadro's number) particles (atoms, molecules, or ions).

Forces that hold atoms together in molecules or compounds, formed by sharing or transferring electrons to achieve a more stable electronic configuration.