Gen. Chem.2 2nd

Thermodynamics

The branch of physics that deals with the relationship between heat, temperature, and other forms of energy.

Thermochemistry

The branch of chemistry that deals with the energy changes involved in chemical reactions.

Work

The creation of motion in the presence of an opposing force.

Energy

The ability to carry out work.

Temperature

Describes the coldness and hotness of an object.

Heat

The flow of thermal energy transferred from a hotter object to a colder object that is in contact with it.

System

The process of chemical reaction of interest.

Surroundings

Anything else outside the system.

Universe

The combination of the system and surroundings.

Isolated system

A system where both matter and energy cannot be exchanged with the surroundings.

Closed system

A system where energy can be exchanged with the surroundings, but matter is prevented from exchanging with the surroundings.

Open system

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

State function

A function that deals with the current condition and does not concern how this condition is attained.

Path function

A function that describes how to arrive at the current condition.

Kinetic energy

The energy in motion, affected by mass and velocity.

Potential energy

The energy of the system affected by its position or composition.

Internal Energy (U)

The sum of the kinetic energy and potential energy.

Exothermic

Processes that release energy in the form of heat to the surroundings.

Endothermic

Processes that absorb energy in the form of heat from the surroundings.

Combustion

The reaction with oxygen to produce small molecules such as CO2 and H2O.

Phase Changes

Freezing, condensation, and deposition.

Dissolution

Some ionic compounds dissociate into ions in water, releasing energy.

Bond Formation

Two unstable atoms may form a stable molecule.

Electron Gain

The energy released when a gaseous atom accepts an electron.

First Law of Thermodynamics

Energy can neither be created nor destroyed, only transformed.

Internal Energy (U)

The total energy possessed by a molecule, consisting of kinetic energy and potential energy.

Heat (q)

(+) heat is absorbed by the system, (-) heat is released by the system.

Work (w)

(+) work is done to the system, (-) work is done by the system.

Joule (J)

The SI unit for heat, work, and internal energy.

Calorie

Another unit for energy, corresponding to the heat needed to raise the temperature of 1 g of water by 1°C.

Expansion Work

The amount of work accompanying expansion, a process in which volume is increased.

Enthalpy

The sum of the internal energy and the product of the pressure and volume of the system.

Change in Enthalpy (ΔH)

The enthalpy change involved in a chemical reaction at standard conditions.

Thermochemical Equation

A chemical equation that indicates the energy, particularly the heat or enthalpy change, that accompanies the reaction.

Exothermic Reactions

Reactions that release energy, indicated by a negative standard heat of reaction.

Endothermic Reactions

Reactions that absorb energy, indicated by a positive standard heat of reaction.

Mole Reaction

The value of ΔrH° corresponds to the energy released or absorbed for 1 mole of reaction.

Calorimetry

The study that deals with the measurement of heats of processes, be it physical or chemical.

Calorimeter

An instrument used to measure heat.

Neutralization

The reaction occurring between an acid and a base to form water and salt.

Hess Law

The enthalpy of reaction is the sum of the enthalpy changes of all steps leading to this reaction.

Rate of Reaction (v)

Describes how fast or slow a chemical reaction is.

Rate of consumption of A

The rate at which substance A is being used up in a chemical reaction.

Rate of formation of B

The rate at which substance B is being produced in a chemical reaction.

Factors Affecting the Rate of Reaction

Various factors that can influence the speed at which a chemical reaction occurs.

Concentration

The amount of a substance present in a given volume or space.

Temperature

The measure of the average kinetic energy of particles in a substance.

Presence of a catalyst

A substance that increases the rate of a chemical reaction without being consumed in the process.

Rate Law

A mathematical equation that describes the relationship between the rate of a reaction and the concentration of reactants.

Reaction Order

The exponent in the rate law equation that indicates the relationship between reactant concentration and reaction rate.

Differential Rate Law

An equation that relates the rate of a reaction to the concentration of a reactant.

Integrated Rate Law

An equation that shows the concentration of a reactant remaining at a given time.

Order of Reactions

The classification of a reaction based on the exponent in the rate law equation.

Zero-Order Reaction

A reaction in which the rate does not depend on the concentration of the reactant.

First-Order Reaction

A reaction in which the rate is directly proportional to the concentration of the reactant.

Second-Order Reaction

A reaction in which the rate is proportional to the square of the concentration of the reactant.