When methane, CH4 burns in oxygen gas, O2, bonds must first be broken in both molecules before new bonds forming the products can be made.
Energy is measured in kilojoules or kJ.
When bonds break, energy must be absorbed from their surroundings. Taking in energy reduces the temperature of the surroundings - this is called an endothermic reaction. This value is always given a positive sign, for example, +345kJ.
When bonds are made, energy is released to the surroundings. Energy that is released to the surroundings is called an exothermic reaction. This value is always given a negative value, for example, -345kJ.
Remember, when a reaction takes place bonds break (endothermic) then bonds are made (exothermic).
Overall, the reaction will be exothermic if more energy is released into the surroundings than was absorbed.
An endothermic reaction will occur overall if, more energy is absorbed from the surroundings than is released.
Bond energy: This is the energy required to break one mole of bonds. The bond energy is also the energy given out when a mole of bonds is formed.
Activation energy: This is the minimum amount of energy required to break bonds to start the reaction off.
If you want to increase the amount of ammonia you make, you have a problem when your reaction mixture reaches equilibrium as the amount of ammonia been produced remains constant.
An important fact about reversible reactions: it is in equilibrium, if you cause a change then it will oppose the change.
You cannot make a reversible reaction go to completion but you can change the conditions so that the equilibrium shifts to the right, producing more product, in this case ammonia.
Since the forward reaction in the production of ammonia is exothermic - gives out heat - by increasing the temperature you are worse off.
This is because the back reaction being endothermic takes the extra energy i.e. it opposes the change. Hence, increasing temperature produces less ammonia!
Pressure is caused by the collision of gas molecules and the container wall.
The fewer molecules you have the lower the pressure. By increasing pressure, the equilibrium mixture will oppose the change - more ammonia will form in order to reduce the pressure.
Adding a catalyst:
Iron acts as a catalyst for this reaction. The catalyst does not affect the equilibrium position since it increases the rate of the forward and back reactions equally, but it does speed up the speed at which equilibrium is reached.