Thermodynamics

Chemistry

Thermochemistry

The study of heat absorbed or released during chemical and physical changes.

Potential Energy

the energy an object has because of its relative position, composition, or condition

Kinetic Energy

the energy that an object possesses because of its motion

Law of Conservation of Energy 

During a chemical or physical change, energy can be neither created nor destroyed, although its form can change.  

Thermal Energy

a type of kinetic energy (KE) associated with the random motion of atoms and molecules

Temperature

A quantative measure of “hot” and “cold”

Heat (q)

The transfer of thermal energy between two bodies at different temperatures.

Heat Flow 

Increases the thermal energy of one body and decreases the thermal energy of the other.

Thermal Equilibrium 

Heat flow will continue until both substances are at the same temperature. 

Exothermic Process

A change that releases heat

Endothermic Process

A change that absorbs heat

Calorie

The amount of energy required to raise one gram of water by 1*C or 1 kelvin

Kilocalorie

The Calorie (with capital C) commonly used in quantifying food energy content.

Joule (J)

The amount of energy used when a force of 1 newton move and object 1 meter.

Heat Capacity (C)

A body of matter is the quantity of heat (q) it absorbs or releases when it experiences a temperature change of 1*C or 1 kelvin

Specific Heat Capacity (c)

The quantity of heat required to raise the temperature of 1 gram of a substance by 1*C or 1 kelvin

Calorimetry

Used to measure the amount of heat transferred to or from a substance

Calorimeter

A device used to measure the amount of heat involved in a chemical or physical process

System

The substance or substances undergoing the chemical or physical change.

Surroundings

All other matter, including components of the measurement apparatus, that serve to either provide heat to the system or absorb heat from the system.

Bomb calorimeter

used to measure the energy produced by reactions that yield large amounts of heat and gaseous products, such as combustion reactions.

Whole-body calorimeters

used to measure the metabolism of individuals under different conditions: environmental conditions, dietary regimes, and health conditions such as diabetes

Nutritional calorie (Calorie)

the energy unit used to quantify the amount of energy derived from the metabolism of foods.

Initial Energy (U)

The total of all possible kinds of energy present in a substance

Enthalpy (H)

the sum of a system’s internal energy (U) and the mathematical product of its pressure and volume

Standard state

A commonly accepted set of conditions used as a reference point for the determination of properties under other different conditions

Standard Enthalpy of Combustion 

The enthalpy change when exactly 1 mole of a substance burns (combines vigorously with oxygen) under standard state conditions.

Standard Enthalpy of Formation

An enthalpy change for a reaction in which exactly 1 mole of pure substance is formed from its constituent free elements in their most stable states under standard state conditions

Hess’s Law

If a process can be written as a sum of several stepwise processes, the enthalpy change of the total process equals the sum of the enthalpy changes of the various steps

Decompositions

The enthalpy changes are proportional to the negative of the enthalpies of formation of the reactants

Recombinations

with the enthalpy changes proportional to the enthalpies of formation of the products