A student may think that only spontaneous reactions take place. In fact, many reactions take place by adding energy during the reaction. This includes many biological reactions that take place in the body. In plants, photosynthesis is fueled by the sun. In cells, the energy of a reaction with a large negative ΔG such as the reaction of ATP may drive a reaction that has a smaller positive ΔG. ATP is produced in cells by using the energy from exergonic spontaneous reaction occurring in the cells.

ATP^4- + H₂O -> ADP^3- + HPO₄^2- + H⁺

ΔG° = -30.5 kJ/mol

Misconceptions about the interrelation of entropy, enthalpy and Gibb's free energy are common with students on their first introduction. This link discusses some of the common questions student have with the interrelationship.

The Second Law / Maxwell's Demon discusses violations of both the first and second law that rule out several complex perpetual motion machines.