We have done this experiment approximately 8,932 times and it never gets old. The supplies are something we always have on hand, the setup is incredibly simple, and the experiment can be as fast or as time consuming as we want (and I'm willing to clean up). When we finish I always carefully carry the full cups to the sink and set them down gently as to not disturb the cloud. I turn the faucet on to a low flow, and the kids love watching the shaving cream cascade down the side as the cups overflow. Without further ado, Rain in a Cup.
Acquire your supplies.
You'll need see through vessel, we chose to use a tall glass. You can use a plastic jar, mason jar, anything that will hold water and is clear.
Water
Shaving Cream
Food Coloring
Small cups (for mixing food coloring & water) *optional
pipettes/droppers *optional
Create a cloud
Fill the glass with water to about an inch or two from the top. The water represents the air in our atmosphere. Spray the shaving cream on top of the water until it reaches just above the top of your cup/jar/vessel. The shaving cream represents rain clouds.
In the small cups mix a couple drops of food coloring with water and stir. (we chose to skip this step)
Make it rain!
For our experiment we dripped the food coloring directly from the bottle onto
the shaving cream. This is mainly because I believe in messes and bright colors, and this accomplished both. It also meant that we needed more food coloring in order to weigh down the "cloud" enough to make it rain. The second (or maybe hundredth, I'm not counting anymore) time we did this experiment the kids dripped the food coloring onto the cloud, then I used a dropper to add water to the cloud. The kids watched underneath to wait for the rain, and were shocked at just how much water the cloud could hold before the rain started to fall.
Recording Sheet
Click on the image to the left to download the PDF file containing the lab report sheet for you to record your observations during this experiment.