Density Lessons and the Oil Spill
Teachers can use the oil spill cleanup efforts as a springboard to discussions and activities related to density!
By Jennifer Sinsel
Last spring, many teachers used the oil spill in the Gulf to teach topics ranging from ocean currents to environmental awareness. Although the situation has improved, cleanup is still a hot topic among the general public – making it a continuing teachable moment for various topics in science.
As students head back to school, teachers can use the spill as a springboard for a discussion of density. Oil floats on water because it is less dense, which allows cleanup crews to contain the spill with booms and collect it from the water surface using skimmer equipment. Elementary students can conduct some simple activities to help comprehend this often misunderstood topic. To illustrate the idea that some materials are less dense than others, obtain four liquids of varying density (corn syrup, salt water, water, and rubbing alcohol are good choices). Color code the liquids with food coloring, keeping the identity of each one a secret until after the activity. Poke clear straws into a raw potato wedge and challenge students to create liquid layers by using an eye dropper to place liquids in the straw. This will likely take several attempts, and students should quickly realize that they need to record their efforts (as all good scientists do) so they don’t forget which combinations have been tried. The corn syrup is the densest, so it must be the bottom layer, followed by the salt water, water, and rubbing alcohol. Once the liquids are layered correctly, the layers will be very distinct and the correct combination will become obvious!
Depending on the age and ability of your class, you might decide to have students figure out the actual density of each liquid. You can use an electronic balance to find the mass of a given volume of each liquid, making sure to zero out the balance to account for the container. To find density, divide the mass by the volume (pure water is 1 g/ml). Students can utilize this same process to make a prediction about the density of motor oil and then figuring its density. As an extension, you can challenge the class to clean up an oil spill by pouring a cup of oil into a tub of water. Provide various materials and allow them to try different methods of cleanup!
For more ideas on teaching density, try the following lesson plans.
Density Lessons and the Oil Spill:
In this lesson students learn about density, mass, volume and ratios. They complete a lab on density to learn how to define mass and volume. They learn a formula for calculating density. The lab has students use objects for experimentation that can make the activity fun and motivating.
Students learn about density by comparing the densities of solids and liquids, calculating density, using a balance to measure liquids, and discussing the significance of density. The lesson involves an experiment to investigate the densities of different objects. It also includes worksheets.
Floating in the Great Salt Lake: A Density Experiment
Using salt students investigate density and buoyancy by experimenting with a variety of mixtures. Students also discuss the mechanics of how and why objects float.
