A thermodynamically unfavorable reaction is one that absorbs energy (endothermic) and decreases the disorder or randomness (entropy) of the system. These reactions do not occur spontaneously and need an input of energy to proceed.
A chemical reaction that absorbs heat from its surroundings.
Negative Entropy Change: This occurs when a system becomes more ordered rather than disordered.
The minimum amount of energy required for a chemical reaction to proceed.