To verify Hooke's law - Hooke's law states that the extent to which an elastic material will change size and shape under stress is directly proportional to the amount of stress applied to it.
An ideal spring is remarkable in the sense that it is a system where the generated force is linearly dependent on how far it is stretched, this behavior is described by Hooke's law. According to Hooke's Law stated above that to extend a spring by an amount dx from its previous position, one needs a force F which is determined by F = kdx. Here k is the spring constant which is a quality of each spring. Therefore, in order to verify Hooke's Law, you must verify that the force F and the distance at which the spring is stretched are proportional to each other (that just means linearly dependent on each other), and that the constant of proportionality is k.