More Density

View of our jars from the top

A fuzzy side view of our jars.

As we continued our exploration of density, we began another investigation using three jars of unknown liquids. The kids didn't know the contents of the jars until after the investigation was completed. Jar #1 contained 60 mL of dish soap (blue liquid). Jar #2 contained 60 mL of baby oil. Jar #3 was nothing but air, which is why I covered it in foil. I didn't want to spoil the surprise. Some kids knew right away there was nothing in it, but some were convinced I had put something in there! The groups all measured the mass of each jar using the triple beam balance. Then they added the jars to the tub of water to observe which was the most dense/least dense. All groups came to the conclusion the blue liquid had the most mass and was the and most dense, while the foil-covered jar had the least amount of mass and was the least dense.

We then discussed why it was so important both the liquids have the same volume. If the volumes are different, we wouldn't know if the blue liquid was, in fact, more dense, or if there was just more liquid in the jar.