IS I students investigated how temperature affects the density of a liquid. A divider is inserted in the container and hot red water is placed on one side and cold blue water on the other. When the divider is removed the blue water slides under the red water. The divider is then reinserted and the water on one side is mixed (results in warm, purple water). When the divider is removed the purple water (of intermediate density) wedges its way between the red and the blue water.
The IS I students had to identify 6 of the above unknown samples using density as the primary physical property. They used water displacement to find the volume and electronic scales to find the mass. Great activity as many of the substances were plastics that had densities that were very close. Accuracy was very important.