Cloud in a Bottle: A Quick Water Cycle Experiment

I learned this neat science experiment in a college Meteorology class. Yes, some of us do get a higher education in talking about the weather 🙂 And I can be a bit obsessed. Anyway, you’ll need:

  • A clear, somewhat flexible water bottle with a cap
  • A few drops of water
  • About 30 minutes of Warmth
  • A match


1) Cap the lid on a water bottle with just a little water left in it. If you have a few rambunctious fourth-graders to help, that’s all the better.

Just some water in a bottle. And some awesome kids.

2) Put the water bottle in a sunny window or some other warm place. Our window wasn’t warm enough on this snowy day, so I put mine near an oven that had just baked cookies for us.

You’ll notice most of your water evaporates. Some of ours had started to condense again on the top, but.. we had no cloud to speak of. That’s because we need dust, smoke, or some other particulate for the water vapor to cling to!

Evaporation in action! And cookies.

3) This one is not photo-documented because the only adult with a camera (me!) needed to perform this step. Uncap the bottle and lay it on its side. Light a match, and just after blowing it out, put its head into the water bottle. This will give your water vapor some particulate to condense upon.

4) Put the lid back on and set the bottle aright. A squeeze of the bottle will create high air pressure, that, depending on the relative humidity and temperature inside the bottle, ought to temporarily make the cloud disappear. Our bottle was cold-ish (because my home was cold-ish today) and the humidity was relatively high, so our cloud only cleared up a bit. But when you quickly let up on the squeezing (lowering the air pressure) a cloud will appear.

Nice looking cloud, eh? If we could lower the air pressure and temperature enough, it would surely rain!

We did this experiment while making a water-cycle diorama that featured precipitation, run-off/percolation, evaporation and transpiration, and condensation. The kids had a blast, and finished their assignments within about an hour and a half (including plenty of time for goofing off and brain-storming.) Happy days. So this experiment is a snap. Give it a try at home, and let me know what your in-house scientists think of it. 🙂

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