If a hockeypuck slides on a perfectly frictionless surface, it will eventually slow down because of its inertia

This is true, if it's a T/F question. This is because inertia is defined by a property of matter by which it continues in its existing state of rest or uniform motion in a straight line, unless that state is changed by an external force. For example, the hockey puck. The player hits the hockey puck with their stick, causing momentum. It will continue moving until the amount of force exerted has decreased/balanced out or until an external force (such as another player) interferes with the force that was exerted.