Exothermic

Energy is released, change in enthalpy will be negative

Hess’s Law of Heat Summation

If the overall equation for a reaction can be expressed as the algebraic sum (+ or -) of the equations of two or more other reactions, then the enthalpy change for that reaction is the algebraic sum (+ or -) of the enthalpy change for those reactions.

Endothermic

Energy is absorbed, change in enthalpy will be positive

Energy Changes According to Highest to Lowest

Nuclear Energy > Electrical Energy > Physical Energy

Thermochemistry

The study of energy changes associated with physical, chemical, or nuclear change

Kinetic Energy

The energy associated with the movement of particles

Potential Energy

The energy stored within particles and the bonds that hold them together

Enthalpy

The sum of all potential and kinetic energies associated with the particles of matter. Enthalpy can also be referred to as thermal energy.

Chemical System

A group of reactants and products being studied

Surroundings

All matter that is not part of the system bur is in contact with the system

Open System

A system in which both matter, and energy are free to enter and leave

Closed System

A system in which energy can enter and leave, but matter cannot.

Calorimetry

Calorimetry is a process by which the energy changes of a system can be measured. A calorimeter is a device that can be used to measure the changes in enthalpy (heat)

Specific Heat Capacity

SHC is defined as the amount of heat required to raise the temperature of 1g of matter by 1 degree Celsius.

State Property

The enthalpy of matter depends on its state. For example, the enthalpy for 100g of water will differ from the enthalpy of 100g of steam. Since temperature and pressure determine the state of matter, we must specify standard conditions to be able to compare enthalpies of different substances.

Standard State

Standard ambient temperature and pressure (SATP) is taken to be 25 degrees Celsius, and 100kPa. Since heat is a state property, it does not matter which path is taken to arrive at some given state.

Molar Heat of Formation

This is the change in enthalpy that accompanies the formation of 1 mole of a compound from its elements.

Rates of Reaction

is a measure of how fast a reaction is taking place, units are (mol/L/s)

Collision or Rate Theory

For a reaction to occur, two particles must collide.