Convection: Shavings in Boiling Water

Fill a larger beaker with water.  Empty your pencil sharpener into the water.  Give it a stir to mix in the pencil shavings (some of them will still float - that's okay).

Place the beaker on a hot plate and turn it on.  The beaker needs to remain on the heat source throughout the entire demonstration.

As the water gets hot, the pencil shavings will make the normally invisible convection currents visible.

The water at the bottom of the beaker is heated.  It then moves to the top of the beaker and the cold water sinks to the bottom of the beaker.  This water is then heated and moves to the top and cooler water sinks to the bottom.  This continues on and on, first heating all of the water, and then maintaining a consistent temperature.