Chem bits. Kinetics and that (:

Endothermic, heat going in. Exothermic, heat given out. (In reaction.)

So, endothermic, as in, takes heat/energy in to make the reaction actually go anywhere. In exothermic, it gives out energy as heat.

Enthalpy change is when we measure heat change at a constant pressure.

Enthalpy is shown by the letter H, and change is shown by Δ/delta. So, a change in is enthalpy is ΔH.

Enthalpy level diagrams show the relative enthalpy levels of the reactants, and products, which, in turn, shows the ethalpy change.

Enthalpy of formation is the enthalpy change when one mole of compund is formed from it's constituent elements, under standard conditions, all reactants and products in standard states.

Enthalpy of combustion is the enthalpy change when one mole of compound is burned in oxygen under standard conditions, all products and reactants in standard states.

Enthalpy change = mass of substance X specific heat capacity X change in temperature.

OR

q=mcΔT

(Q = enthalpy change)

In a calorimeter, fuel is burnt to heat a known mass of water (m), and then measure the temperature at the beginning and throughout, to get the change in temperature (ΔT) and the standard heat capacity can be used, or one is given, and then q=mcΔT can be used.

The calorimeter, and measurement of enthalpy change can be made more accurate by preventing heat loss. This can be as simple as adding a lid, draught screen, and insulation around the beaker.

To measure enthalpy changes in solution it is normally in a polythene cup. These are insulators, so heat loss will be reduced, and the heat capapcity is low, and this means they don't absorb much heat, and it all stays in the solution.