Hands On: Water Cycle in a Bag
Big Idea
Water never truly "disappears"—it just changes form and moves to different places. This activity lets you see the entire global water cycle happen right in your window.

Materials

• Plastic Bag
• Water
• Blue Dye (optional)
• Sharpie
• Tape or way to attach bag to an outside window

What to Do

1. The Artwork
   • Use the Sharpie to draw a sun in the top corner, some clouds at the top, and waves at the bottom of the bag.
2. The Ocean
   • Fill the bag with about 2 inches of water (add a drop of blue food coloring so it's easier to see).
3. The Seal
   • Zip the bag shut tightly so no air can get out.
4. The Sun Power
   • Tape the bag to a sunny window.
5. The Observation
   • Check the bag every hour. You will see "mist" form on the sides and eventually "rain" droplets sliding back down into the ocean.

What You’ll Notice

• The water at the bottom stays blue, but the droplets on the side are clear.
• When the sun hits the bag, it gets foggy inside.
• The droplets get bigger and heavier until they can't stay up anymore and drip down.

What’s Really Happening (Parent Explanation)
The sun provides energy that turns the liquid water into water vapor (Evaporation). When that vapor hits the cooler plastic at the top, it turns back into tiny liquid drops (Condensation), forming a "cloud." When the drops get too heavy for the plastic to hold, they fall back down (Precipitation), returning to the "ocean" (Collection).

Key Takeaway for Kids

• The Sun is the "engine" that makes the water move.
• Water can be an invisible gas (vapor) or a visible liquid.
• The water on Earth today is the same water that has been here for billions of years!

Optional Discussion Questions

1. Where did the "fog" on the bag come from if we didn't touch the water?
2. What would happen to our cycle if we moved the bag to a dark, cold closet?
3. Why do the water drops eventually fall back down instead of staying at the top?

Why This Matters
This activity scales down a planet-sized system into something a child can hold. It helps them realize that the "disappearing" puddle on the sidewalk isn't gone—it's just moving to the next stage of the story!