Make a rain cloud in a jar

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During the course of our weather unit we learned about the water cycle, how clouds form, and of course, rain. We thought it would be fun to make a rain cloud in a jar as part of our learning about rain.

Note: You’ll find more weather-related activities on my Weather Unit Study page.

How does rain form?

As part of the water cycle, water in oceans, lakes, and rivers turns into gaseous water vapor when heated by the sun in a process called evaporation. The evaporated water rises into the air. As it goes higher, it encounters cooler and cooler temperatures, which causes the water vapor to condense back into liquid water droplets. When enough of these liquid water droplets come together, they form a cloud.

The liquid water droplets that make up a cloud are very, very small – about 1/100 mm. At this size, the water droplets are so small they practically float on air. They are far too small to drop to the ground as rain.

However, water droplets inside a cloud are always moving and bumping into each other. Sometimes, water droplets collide and join together, forming bigger water droplets. If these droplets reach at least 1/10 mm in size, they are big enough to fall to the ground as rain.

Making a rain cloud in a jar

We decided to model the rain formation process by making a rain cloud in a jar. To do this, we gathered the following materials:

Shaving cream
Clear jar
Water
Container of water dyed blue (you must dye the water so it will be seen when it falls through the rain cloud)
Pipette (we own these pipettes but I also love the one in this set)

We started by filling our jar nearly to the top with the plain (non-dyed) water. We filled it until there was only about 2″ of space between the top of the shaving cream and the top of the jar. Then we squirted shaving cream on top of the water in order to make our “cloud.” We allowed the shaving cream to fill up over the top of the jar for a fluffy, cloud-like look.

Then, we used our pipettes to drip blue water onto our rain cloud.

At first, nothing much happened. You can liken this to a cloud being filled with water droplets, but the water droplets are not yet big and heavy enough to fall to the ground as rain.

However, we kept adding blue water to our cloud, and eventually the cloud became saturated enough to start “raining.” We saw beautiful streaks of blue water falling from the cloud into the water below.