Consider the object attached to a spring in the following animation.  Assume that the spring is ideal (i.e. spring has no mass and the force required to stretch or compress the spring is given by Hooke's law).   There are no external forces acting on the object-spring system.

Is the object a closed system or an open system?

Is the object-spring system a closed system or an open system?

How is the work done by the spring on the object related to the potential energy of the spring-object system?