Water Cycle Column: Is Rain Pure?

When birds and animals drink from lakes, rivers, and ponds, how pure it is? Are they really getting the water they need, or are they getting something else with the water?

This is a great experiment to see how water moves through natural systems. We’ll explore how water and the atmosphere are both polluted and purified, and we’ll investigate how plants and soil help with both of these. We’ll be taking advantage of capillary action by using a wick to move the water from the lower aquarium chamber into the upper soil chamber, where it will both evaporate and transpire (evaporate from the leaves of plants) and rise until it hits a cold front and condenses into rain, which falls into your collection bucket for further analysis.

Sound complicated? It really isn’t, and the best part is that it not only uses parts from your recycling bin but also takes ten minutes to make.

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Here’s what you need:

• three 2-liter soda bottles, empty and clean
• razor with adult help
• scissors
• tape
• ruler
• 60 cm heavy cotton string
• soil
• water
• ice
• plants
• drill and drill bits
• fast-growing plant seeds (radish, grass, turnips, Chinese cabbage, moss, etc.)

Here’s what you do:

Download Student Worksheet & Exercises

Make sure your wicks are thoroughly soaked before adding the soil and plants! You can either add ice cubes to the top chamber or fill it carefully with water and freeze the whole thing solid. If you’re growing plants from seeds, leave the top chamber off until they have sprouted.

You can add a strip of pH paper both inside and outside your soil chamber to test the difference in pH as you introduce different conditions. You can check out the Chemical Matrix Experiment and the Acid-Base Experiment also!) What happens if you light a match, blow it out, and then drop it in the soil chamber? (Hint – you’ve just made acid rain!)

Do you think salt travels with the water? What if you add salt to the aquarium chamber? Will it rain salty water? You can place a bit of moss in the collection bucket to indicate how pure the water is (don’t drink it – that’s never a good idea).

Exercises

1. Do you think salt travels with the water?
2. What if you add salt to the aquarium chamber? Will it rain salty water?
3. What happens if you light a match, blow it out, and then drop it in the soil chamber? (Hint – you’ve just made acid rain!)

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