Aluminium rod and heat

Jan´s experiment from the Czech team
Pierce the middle of an aluminum rod, slightly above the center of gravity. Hang the rod on a revolving stand. Stick a glass-headed pin in a cork stopper, and use this as the axis of rotation. Put the rod in the horizontal position. Make one side hot. As the rod is heated, this raises the energy of particles and thus increases their weight. So the heated arm is heavier and sinks down :-).
Truth be told. Heat extends the aluminum rod; the center of gravity moves to cause a new rod position, with a stable center of gravity below the point of suspension.