Urban Ecology

Pollution Spread

What it does

This experiment shows how a small amount of pollution spreads over a large area.

What you need

• One-gallon glass jar
• Measuring cup
• Food coloring in a bright color (like red or blue)

What to do

1. Pour a cup of water into the jar.
2. Drop in about two drops of food coloring.
3. Stir the water so that the food coloring spreads through the water.
4. Slowly add and stir in water, one cup at a time. Count how many cups it takes to make all the color disappear.

What it's all about

The coloring probably won’t disappear until you have added about 7 cups of water, even though there were only two drops of food coloring. The color gets lighter and eventually disappears because the food color molecules spread out further and further as you add more water. They finally spread out so far that they are invisible because of their tiny size. The same thing happens to pollutants. They spread through water and air until you cannot see them anymore. But, like the food coloring, they still exist and can still do damage. For instance, animals and people may be harmed by drinking water many miles downstream from a source of pollution.

Remember, be sure you have a parent, teacher, or other adult help you!

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