Water Cycle in a Bag

Seattleites are overly familiar with the water cycle. Specifically the precipitation portion. Yet, carry an umbrella on the streets and you might as well wear a sign proclaiming “Tourist!!”. This weekend during our first soccer games (three of them…how is this possible given I only have TWO children?), my Tennessee transplanted friend commented on the rows of parents shielding themselves from the sweltering (70 degrees) heat, “This is the only time you ever see Seattle people with umbrellas…when it’s sunny.”.  Hahaha! It’s so true!

Back to the point. This cycle in Classical Conversations we’ll be memorizing the natural cycles and since it’s our second time through (how is it possible we’re entering year 4 of homeschooling?), I thought we’d add to our memory work with a little hands on example. I found a great idea (thanks Pinterest!) for a Water Cycle in a Bag that only needed a few supplies, all of which I had in the house already. Easy science that costs nothing? Boom. I’m in.

You’ll need a sandwich sized Ziploc baggie, 1/4 cup of water, a smidge of blue food coloring, sharpie (for drawing on the bag), and a piece of tape. Draw a sun and a cloud on the outside of the baggie, add the food coloring to your water, then the water to your baggie. Tape it to a window where you’ll get sunshine and watch the magic!

If you want to be really fancy, you can label your bag with the various parts of the water cycle, but I just talked to my kids as the process got going. Tiny droplets as water evaporates as it’s heated by the sun. The water turns from a liquid to a gas, but with nowhere to escape from the bag, it cools and turns back into a liquid (condensation).

The droplets that have condensed will continue to grow in size as more water turns to gas, and back to liquid. Usually this process is happening high in the sky, and we know it’s happening because clouds form as a result of condensation.

You can see that our droplets are getting larger. Actually, we were able to watch the condensation happen right before our eyes. Pay close attention to the video and you’ll see the droplets joining together and growing! It’s alive!! Run for your lives!

When the droplets get too big and heavy, they begin to drip down the sides of our bag, leaving trails behind. Precipitation happens exactly the same way when water droplets within clouds get too heavy and fall back to earth as rain. Conveniently, our “rain” fell right beneath our cloud drawing.

Who knew water evaporating, condensing and precipitating could be so fascinating? My kids check on our baggie about a dozen times a day and are making all kinds of connections to how temperature affects evaporation based on their observations. This little project has prompted lots of great questions and discussion — which for kids, is what science should be all about anyway!