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Weather Academy: Water Cycle in a Bag

Published: May. 23, 2022 at 6:21 AM CDT
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MONROE, La. (KNOE) - Last week on the Weather Academy, we went back to the basics and talked about the water cycle. And today, we’re gonna be doing a hands-on experiment demonstrating the water cycle on a smaller scale.

What you’ll need:

  • Plastic zip lock-style bag
  • Permanent marker(s)
  • Water
  • Blue food coloring
  • Clear tape

Steps:

  1. Decorate the bag. draw a sun towards the top of your bag and a few clouds, and then draw waves to represent water at the bottom of the bag.
  2. Add the water and the food coloring. You want about an inch of water at the bottom of the bag. Seal up the ziplock tight.
  3. Hang up the bag using the tape in a very sunny window.
  4. Wait and observe!

The wait time will range anywhere from 2 hours to 1 day, depending on the amount of sunshine.

Eventually, you will begin to see droplets of water sticking to the side of the bag. Some of these will be up high (in the clouds), while other droplets will be on their way back down (like rain).

Why does this happen? It’s because the water in the bag is being heated up against the sunny window. That water turns into a gas through a process called evaporation. In nature, evaporated water vapor lifts up into the atmosphere, but it has nowhere to go in our bag, so it ends up sticking to the sides of the bag, turning back into a liquid as condensation. That condensed water then slides back into the pool of water below as “rain.” This cycle will continuously repeat, so you can leave it up and check on it as often as you’d like. You may even get the chance to teach someone else about the water cycle.

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