For a chemical reaction to occur, what must happen?

For a chemical reaction to occur, it is essential that particles collide with sufficient energy and in the correct orientation. This concept is part of the collision theory, which states that for a reaction to happen, the reacting particles must collide not only with enough energy to overcome the activation energy barrier but also in a manner that allows for the proper rearrangement of atoms.

When particles collide with adequate energy, they can break the existing bonds and form new ones. The orientation of the particles during the collision is also critical; if the molecules do not align properly, even a high-energy collision may not lead to a successful reaction. For example, think of a puzzle: the pieces may have the right shape (energy) but must fit together (orientation) to complete the image (reaction).

This understanding of the conditions necessary for effective collisions highlights why other options are not suitable for describing the requirements for a successful chemical reaction.