Convection Currents

We could plainly see that the coloured water first rose to the surface.

At first, the jar floated on top of the water, so we added some old coins.
Their combined weight made the jar successfully sink to the bottom
 of the water filled container.

To investigate convection currents, we filled a large container with clear cold water, and filled a small jar with hot water mixed with dye.  We carefully lowered the jar into a container and watched what happened.