A normal ice cube is less dense than liquid water, but a deuterium oxide ice cube is more dense than liquid water.
An H2O ice cube is less dense than liquid water, but a D2O ice cube is more dense than liquid water.
Introduction to the floating squares demonstration shows the preparation of the square of paper rubbed with graphite on one side.
A paper square rubbed with graphite on one side is placed at the interface between two immiscible liquids (carbon tetrachloride and water).
Solid sulfur is placed in a beaker and then heated in a bunsen burner flame. As the solid is heated, it begins to melt and a reddish brown liquid forms.