Enthalpy is a measure of the heat energy in a chemical system.

Enthalpy change = Products(enthalpy) - Reactant(enthalpy)

q = mc(change in)T
q = heat energy (J)
m = mass of the surrounding (m)
c = specific heat capacity of the surrounding (J g^-1 K^-1
T = temperature

Reasons why Experimental is different to Data book

• heat loss in surrounding like air
• imcomplete combustion
• evaporation
• not standard solution

• The Standard enthalpy change of atomisation
• the enthalpy change that takes place for the formation of one mole of gaseous atoms from the elements in its standard state under standard condition
• (Endothemic)

• Lattice enthalpy
• the measure of the strength of ionic boning in a giant ionic lattice.
• the enthalpy change that accompanies the formation of one mole of an ionic compound from its gaseous ions under standard conditions
• (Exothermic)

• The enthalpy change of neutralisation
• the enthalpy change that accompanies the reaction of an acid by a base to form one mole of water under standard conditions with its reactants and products in standard state

• The enthalpy change of Combustion
• the enthalpy change that takes place when one mole of a substance reacts completely with oxygen under standard conditions with the reactants and products in standard state
  

• The enthalpy change of formation
• the enthalpy change that takes place when one mole of a compound is formed from its element under standard condition, with its reactants and products in standard state

• The Standard enthalpy change of Reaction
• the enthalpy change that accompanies a reaction in molar quantities shown in the equation under standard condition, with the reactants and product in standard state

• First ionisation energy
• the enthlapy change required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous +1 ions
• (Endothermic)

• First electron affinity
• the enthalpy change that accompanies when one electron is added to each atom in one mole of gaseous atoms to form one mole of gaseous -1 ions
• (Exothermic)
• all electron affinities after the first are endothermic

• Enthalpy change of solution
• the enthalpy change that takes place when one mole of a solute is dissolved in a solvent (water)

• Enthalpy change of hydration
• the enthalpy change that takes place when gaseous ions are dissolved in water to form one mole of aqueous ions