AFOQT Practice Test

The primary cause of chemical reactions is the change in bonding structure due to electron exchange. Chemical reactions occur when the atoms in reactants interact, leading to the formation or breaking of bonds. This interaction often involves the transfer or sharing of electrons between atoms, which alters their bonding configurations and consequently results in the formation of new substances.

The other factors listed, such as temperature changes, physical changes, and concentration, can influence the rate or direction of a chemical reaction but do not fundamentally cause the chemical changes themselves. Temperature can affect the energy and movement of particles, concentration can influence how often reactant molecules collide, and physical changes refer to alterations in state or appearance without changing the substance itself. However, the intrinsic change in bonding due to electron dynamics is the root cause of the reactions that create new chemical substances.