Chem mid term 1

Thermodynamics

The branch of physical science that deals with the relations between heat and other forms of energy.

Kinetic Energy

The energy an object possesses due to its motion.

Free Energy

The energy of a system that can perform work at constant temperature and pressure.

Enthalpy

A measure of the total energy of a thermodynamic system, including internal energy and the energy required to make room for it.

1st Law of Thermodynamics

Energy cannot be created or destroyed, only transformed from one form to another.

System

The part of the universe that is being studied, separated by boundaries.

Surroundings

Everything outside the system that can exchange energy with it.

Expansion Work

Work done by a gas during expansion, calculated as w = -PextΔV.

Exothermic Reaction

A chemical reaction that releases heat, resulting in a decrease in enthalpy.

Endothermic Reaction

A chemical reaction that absorbs heat, resulting in an increase in enthalpy.

Hess’s Law

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

Bond Dissociation Energy (BDE)

The energy required to break a bond in a molecule.

Calorimetry

The science of measuring the heat of chemical reactions or physical changes.

Specific Heat

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

Standard Temperature and Pressure (STP)

Conditions defined as 0°C (273.15 K) and 1 atm pressure.

Entropy

A measure of the randomness or disorder of a system.

Second Law of Thermodynamics

In any energy exchange, if no energy enters or leaves the system, the potential energy of the state will always be less than that of the initial state; in other words, the entropy of an isolated system always increases.

Gibbs Free Energy (∆G)

A thermodynamic quantity that combines enthalpy and entropy to predict the spontaneity of a process.

Reaction Rate

The change in concentration of a reactant or product per unit time.

Rate Constant (k)

The proportionality constant that relates the rate of a reaction to the concentration of the reactants in the rate law.

Rate Law

An expression that relates the rate of a reaction to the concentration of its reactants; formulated based on experimental data.