Pollution is bad; if any of your students don’t know that, ship ‘em back to first grade immediately. Water pollution is also bad; see previous suggestion. Water pollution not only pollutes the water itself, it can also affect the flora and fauna around the body of water. This Demo Science science demo will give your students a solid visual representation of just how long the effects of water pollution can last.
Emmet Otter’s Jug Band Science Project
This week’s supply trifecta: a one-gallon glass jug, water (at least enough to fill your jug), and some food coloring. I feel that red is the most visually effective, but feel free to use whatever color you like.
Pour about a half-cup of water into the jar, then stir in two or three drops of food coloring. Keep adding water, roughly a cup at a time, until the food coloring is completely dissipated.
If you do it all right, the food coloring should be more or less invisible after the seventh cup of water. Why is that? And what does that tell us about environmental water pollution?
It’s A Metaphor, Kevin
The food coloring represents pollutants—industrial discharge, chemical spillage, etc.—in a water source like a river or stream. (Or a jar, in this case.) The dye was more visible at first because its molecules are close together. As you add more water, however, those molecules spread out as they disperse through the water. More and more water spreads them out more and more, and finally the colored molecules are too far apart to be visible.
This is actually a fairly accurate demonstration of how a lot of water pollution actually occurs. Pollutants enter the water in a concentrated “cloud”, making them easy to see and the source easy to spot (usually). The further downstream the pollutants flow, the more they mix in with the river water, or are ingested by some creature or another, rendering the pollution harder and harder to see.
However, the food coloring molecules don’t just go away because they’re spread farther out. Nor does pollution in water magically go away once it becomes “invisible”. Those pollutants can remain in the ecosystem for years, harming plants and animals miles away from the initial source of the pollution.