5. How would you use information that we have learned over the last two lessons to revise our working model to explain how fuel makes a car engine work (and therefore a car move)? Use the diagram below to help you verbally describe any changes you would make.
Thermochemistry
Thermochemistry can be considered as a branch of thermodynamics that deals with the connections between warmth, work, and various types of energy, formed because of different synthetic and actual cycles. Thermochemistry describes the energy changes that occur as a result of reactions or chemical changes in a substance.
Exergonic Reaction
The term exergonic is derived from the Greek word in which ‘ergon’ means work and exergonic means ‘work outside’. Exergonic reactions releases work energy. Exergonic reactions are different from exothermic reactions, the one that releases only heat energy during the course of the reaction. So, exothermic reaction is one type of exergonic reaction. Exergonic reaction releases work energy in different forms like heat, light or sound. For example, a glow stick releases light making that an exergonic reaction and not an exothermic reaction since no heat is released. Even endothermic reactions at very high temperature are exergonic.
The engine works on a closed thermodynamic cycle. The piston makes four strokes. The first stroke is the suction. In this stroke the charge (air-fuel mixture in case of SI Engine and air only in case of CI engine) is taken in. After the suction begins the compression stroke. in this sroke the charge is compressed, this raises the temperature and pressure. At the end of compression, the heat is added (in case of Si engine engines heat is added at constant volume and in case of CI engines some part of heat is added at constant volume and some at constant pressure) by igniting the fuel.
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