Teaching Strategies

Oil Slick
An experiment that uses an environmental-protection method

By Janice VanCleave

Your seventh- and eighth-grade students are most likely aware of the disastrous consequences that oil spills can have for the environment. During this Keep America Beautiful Month, have students try a variation on a method used by pollution-control experts to clean up a spill.

Clear, medium-sized drinking glass
Tap water
6–8 metal washers
Empty prescription container, large enough to hold the washers
Two 24-inch (60-cm) pieces of string
1/4 cup (63 ml) cooking oil
Small bowl

Fill the glass 3/4 full of water.
2. Place two or three washers in the empty medicine container.
3. Tie the pieces of string together. Tie the other ends of the strings around the top of the medicine container to form a loop.
4. Place the container, with its two or three washers, in the glass of water and support it upright with the loop.
5. Continue to add washers until the top of the container sinks just below the surface of the water. Remove the container and pour out any water but leave the washers.
6. Pour the oil into the glass, then slowly lower the weighted container into the glass.
7. Holding the loop, support the container so that its top is just below the surface of the oil.
8. When the container fills, raise it out of the glass, pour its contents into the bowl, and observe the liquid.
9. Repeat the procedure until all the oil is removed from the glass.

The first few collections will be pure oil, then a mixture of oil and water will be collected. Tell students that, fortunately, oil as a pollutant remains highly visible. It can be collected because it floats on the water's surface rather than dispersing into the water. Oil and water cannot mix together into one unified substance. The oil will eventually separate from the water, even if they are stirred or shaken together rapidly.
One method of environmental oil retrieval is very similar to this experiment. An oil drum is weighted so that its top is just beneath the wurvace. The floating oil then flows into the drum and is pumped out. With this method, much of the damage that an oil spill can cause will be averted.

Excerpted with permission of the publisher John Wiley & Sons, Inc., from Janice VanCleave's 202 Oozing, Bubbling, Dripping, and Bouncing Experiments. Copyright 1996 by Janice VanCleave.

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