This simple activity is the ultimate rainy day project. It's part art, part science, and guaranteed to get the kids excited about the dreary weather that's keeping them from playing outside. To get started you'll need some clear containers, water, food coloring, a dropper, and shaving cream. Make sure you get the old fashioned kind of shaving cream. The fancy gel type is no good for our purposes.
Tackle the science portion first. Fill your chosen vessel (we used glass measuring cups and mason jars) about two-thirds full of water. Add a puffy layer of shaving cream on top. Explain that the water represents air and the shaving cream represents a cloud, which is made up of lots of tiny droplets of water or ice. Mix some of the blue food coloring with water and add it, a few drops at a time, to the top of the shaving cream. The result will be blue rain. For faster rain, try non-diluted food coloring.
Now it's time for some hypothesizing. Ask your children to think about why clouds are able to float. (The short answer is that the water and ice droplets are very light.) Why does your child think clouds sometimes make rain? You can keep the answer to this one simple, too. The bigger the cloud gets, the more the water droplets bang together and grow. Eventually they get so heavy, they fall to the ground.
Challenge older kids to flex their critical thinking skills a bit more. The truth is, nobody knows exactly how clouds make rain. Scientists think it has to do with the water droplets freezing onto tiny particles of dust or bacteria inside the cloud, called cloud seeds, causing them to become heavy and fall to the ground. If you really want to blow your kiddos' minds, mention that people sometimes try to make it rain by sending planes to shoot dust into clouds, a process known as cloud seeding.
At this point, your children will be pretty antsy to take a crack at making rain. Hand over the dropper and let them try it. We used a leftover medicine dispenser instead of a traditional dropper. Since my three-year-old son pushed quite a bit harder than I did, he was able to observe the effects of varying amounts of pressure on the shaving cream and water.
When the thrill starts to wear off making rain, you can add a whole new level of fun by introducing some color mixing. Set up a few more jars of food coloring and water and let your child experiment.
What I like about this technique is that, for the most part, the colors stay separate on top of the shaving cream.
But below the shaving cream, they swirl and mix together to create beautiful new hues. Seeing blue and red on top and purple underneath really reinforces the color mixing concept.