Water Cycle in a Bag Experiment
Seal water in a zip bag, tape it to a sunny window, and watch evaporation and condensation happen before your eyes. The entire water cycle, miniaturized.
What You'll Need
- 1Zip-lock bag (quart size)
- 2Permanent marker
- 3Water
- 4Blue food coloring
- 5Tape
- 6Sunny window
What You'll Need
A quart-size zip-lock bag
Permanent marker for drawing
Water (about a quarter cup)
Blue food coloring
Tape
A sunny window
How to Play
Draw a water cycle on the bag: ocean at the bottom, clouds at the top, arrows for evaporation and rain.
Add water and a drop of blue food coloring. Seal tightly.
Tape the bag to a sunny window at eye level.
Check every few hours: "Droplets at the top! That's condensation — like clouds!"
Watch droplets grow and run down: "That's precipitation — rain in our bag!"
Leave it for several days. The cycle repeats.
Discuss: "The water keeps going around — just like on Earth."
The Science Behind It
The sun heats the water in the bag, causing evaporation — liquid water turns into water vapor (gas). The vapor rises to the top of the bag where it's cooler, and condenses back into tiny water droplets (like clouds). When the droplets get big enough, they run down the sides (precipitation). This is the exact same process that creates weather on Earth, just miniaturized in a bag on your window.
Tips
South-facing windows get the most sun. More sun = faster, more dramatic results.
The water cycle diagram on the bag helps your child connect what they see to the vocabulary: evaporation, condensation, precipitation.
Check the bag first thing in the morning and again in the afternoon. Temperature changes throughout the day drive the cycle.
Ask: "Where does rain come from?" after this experiment. Your child will be able to explain it.
Leave the bag up for a full week. Sustained observation deepens understanding.
Age Adaptation Tips
School-age kids can take more ownership. Let them lead the activity, experiment with variations, and explain what they learned.
Frequently Asked Questions
How long does this activity take?
This activity takes about 15 min, with 5 min of preparation time beforehand.
What materials do I need?
You'll need: zip-lock bag (quart size), permanent marker, water, blue food coloring, tape, and 1 more item.
What age is this activity for?
This activity is designed for 5-8 years. You can adapt it for younger or older children by adjusting the complexity.
Can this be done indoors?
This activity is designed for indoor play, making it perfect for rainy days or when you're staying inside.
How difficult is this activity?
This is an easy activity that requires minimal setup and supervision. Great for busy days or when you need something quick.
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