Force can change the shape of an object, so the tension makes the spring elongate;

When the spring is stretched, it is elastically deformed, and the elastically deformed object will exert a force on the object in contact with it, that is, elastic force; Moreover, the longer the spring is pulled, the greater the elasticity and the more laborious it is to pull.

So the answer is: force can change the shape of an object; The elongation of the spring is proportional to the tension.