Efficiency (20min) - enthalpy of combustion, useful energy, heat transfer 

Efficiency describes the energy that a certain system can extract and make useful from the energy source. Any system that uses energy from fuel has an efficiency rating. It is important to note that efficiency is not equal to effectiveness since effectiveness is solely based on the principle making use of energy to do the right goal rather than how well it completes the goal. In order to calculate the efficiency of the transfer of heat from the system versus the surroundings, determine both the energy released or absorbed and compare them to each other using the formula energy output divided by energy input followed by multiplying 100%. The energy output also known as the surrounding is represented by "Q" since it is the medium that is absorbing the energy while the energy input is the system that is represented by "delta H" since it is the compound that is releasing energy. Finding out how much of this release of energy actually got measured by the medium absorbing that heat is the goal of efficiency calculations.