Chapter 6 Thermochemistry Lecture Notes

A collection of flashcards covering key concepts in Thermochemistry, highlighting definitions and essential principles.

Energy

The capacity to do work.

Work

The result of a force acting through a distance, calculated as w = F x d.

Thermodynamics

The study of energy and its transformations.

Kinetic Energy

The energy associated with the motion of an object, calculated as KE = ½mu².

Thermal Energy

The energy associated with the temperature of an object.

Potential Energy

The energy associated with the position or composition of an object, calculated as PE = m x g (acceleration due to gravity) x h (height)

Chemical Energy

The energy associated with the relative positions of the electrons and nuclei in atoms and molecules.

State Function

A property that is independent of the path taken to reach that specific state.

Law of Conservation of Energy

The law stating that energy can neither be created nor destroyed, only transformed.

Exothermic Process

An energy transfer where energy flows out of the system to the surroundings (q < 0).

Endothermic Process

An energy transfer where energy flows into the system from the surroundings (q > 0).

Internal Energy (E)

The sum of all energies within the system, a state function.

Heat Capacity

A measure of a system’s ability to absorb thermal energy with changing temperature.

Enthalpy (H)

The sum of the internal energy and the pressure-volume product of a system. H = E + PV

Molar Heat Capacity (cp)

The amount of heat required to raise 1 mole of a substance by 1 °C.

Specific Heat Capacity (cs)

The heat required to raise the temperature of 1 gram of a substance by 1 °C.

Hess' Law

The principle that if a chemical reaction can be expressed as a series of steps, the enthalpy change for the overall equation is the sum of the steps.

Calorimetry

The measurement of heat transfer in chemical reactions.

Standard Enthalpy of Formation (ΔH°f)

The change in enthalpy when 1 mole of a compound forms from its elements in their standard states.

Isolated system

no contact of any type with surroundings

Closed system

energy (heat) can be exchanged with surroundings

Open system

energy and matter can be exchanged with surroundings

What is the sign if a system gains thermal energy?

positive

What is the sign if a system loses thermal energy?

negative

what is the sign if work is done on the system?

positive

what is the sign if work is done by the system?

negative

what is the sign if energy flows into the system? (change in internal energy/delta E)

positive

what is the sign is energy flows out of the system? (change in internal energy/delta E)

negative