AP Chemistry: UNIT 5 THERMOCHEM

Energy

The ability to do work or produce heat.

Joules

The unit of measurement for energy.

Law of Conservation of Energy

Energy can be converted from one form to another but can be neither created nor destroyed.

Potential Energy (PE)

Energy due to position or composition; stored energy.

Kinetic Energy (KE)

Energy due to the motion of an object; calculated using the formula KE = ½ mv².

Heat Transfer

The transfer of energy between two objects due to a temperature difference.

Work

The product of force acting over a distance; defined as work = force x distance.

System

The part of the universe on which one wishes to focus attention.

Open System

A system that can exchange mass and energy with its surroundings.

Closed System

A system that allows transfer of energy (heat) but not mass.

Isolated System

A system that does not allow the transfer of mass or energy.

Exothermic Reaction

A reaction that results in the evolution of heat, where energy flows out of the system.

Endothermic Reaction

A reaction that results in absorption of energy from the surroundings; heat flows into the system.

Thermodynamics

The study of energy and its interconversions.

First Law of Thermodynamics

Energy of the universe is constant; energy cannot be created or destroyed.

Enthalpy (ΔH)

The heat content of a system that is defined as H=E+PV.

Calorimetry

The science of measuring heat associated with a chemical reaction.

Bomb Calorimeter

A device used in constant-volume calorimetry to measure energy in reactions.

Hess's Law

The total enthalpy change for a reaction is the same regardless of whether it occurs in one step or multiple steps.

Standard Enthalpy of Formation (ΔHf°)

Change in enthalpy when one mole of a compound forms from its elements in their standard states.

Standard State

The precise reference state for a substance, typically at 1 atm and 25°C.