Have everyone sit their chairs in a circle, as close together as they can while still being side by side. Pick one person to stand, which leaves an empty seat. The standing person must try to sit in the chair, however the person to the left of the chair is going to take it. That moves the empty chair, the new person to the left will sit in that chair, and so on around the circle.
If the leader calls "switch", the people sitting in the circle will switch directions and start taking the empty chair to the right. Remind the participants to only move if the chair next to them is empty. Remind them also not to put their hands down on the chair (as this can result in injury), only move their seat.