A piece of rubber under an ordinary stress can display 100% strain; yet when unloaded, it returns to its original length. Does this show that the restoring forces in a rubber piece are strictly conservative?
In case of rubber, the loading curve of stress versus strain graph does not coincide with unloading curve because of elastic hysteresis. Hence work done by restoring force over one complete cycle of loading and unloading is not zero. Hence restoring forces in a rubber piece are not conservative.
What do you understand by intermolecular forces?
Intermolecular force is the force between the molecules of the substance is called intermolecular force.
There is a dipole-dipole interaction between the molecules.
Adhesive force is the attractive force between two unlike molecules. They are caused by forces acting between two substances like electrostatic force (attraction due to opposing charges), mechanical force etc.