Models in Technology and Science by Bernie Zubrowski.
The movement of different liquids is observed in a set of mystery bottles. Students carry out solubility tests and weigh equal volumes of the liquids to identify what the liquids are. These experiences are used to introduce the concept of density. A second set of bottles each having a liquid and several balls of different densities is also investigated. The densities of the liquids compared to those of the balls are determined. A homemade Lava Lamp is made from mineral oil and two kinds of rubbing alcohol.