We are currently smack dab in the middle of the unrelenting afternoon thunderstorms that define summers in the South. What better time to learn about the Water Cycle, right?
Below, you’ll find three different experiments to help demonstrate and explain the Water Cycle!
Making It Rain, Part One
This is a great demonstration for little hands. There’s minimal mess and necessary assistance from grown-ups. I really like using this one with toddlers!
Materials:
- A shallow dish (or any kind of pan, tray, bowl, or water-holding vessel)
- Cotton balls
- Water
Procedure:
- Fill your water-holding vessel with water. An inch or so should do it.
- Take a cotton ball “cloud” to explore. Note that the cotton ball is fluffy and doesn’t weigh much. It’s also very dry.
- Slowly, dip the cotton ball “cloud” into the water, allowing the water to slowly soak the cotton ball. Now your cloud is filled with rain-to-be. Note that it feels heavy and may have even changed shapes.
- Lift the cotton ball out of the water. The cotton ball is so saturated that water droplets will begin to fall back into the water-holding vessel. The more saturated, the faster the rain drops fall.
- Explain that this is [roughly] how the water cycle works. Not sure how the water cycle works exactly? No worries. Read on!
Making It Rain, Part Two
This has been a favorite of mine in the classroom for years. I’ve used it for demonstrations with second and third graders, who’ve equally loved it. The food coloring can stain, so make sure to take precautions for that!
Materials:
- Clear cup or jar (plastic or glass is fine)
- Shaving cream
- Water
- Food coloring
Procedure:
- Fill your cup with water, leaving a small space at the top for your shaving cream.
- On top of the water, squirt shaving cream to create a nice, fluffy “cloud”.
- Carefully add drops of food coloring to the top of your shaving cream cloud.
- As the cloud gets heavier with the added food coloring, it will slowly begin to “rain” food coloring down into the cup. (Make sure you’re adding the food coloring slowly. Once it makes its way through the shaving cream, it will spread through the water quickly. If you’ve added too much, the water will rapidly change color and the experiment gets decidedly boring instantly!)
Making It Rain, Part Three
This is a more advanced demonstration that can be appropriate for most elementary school ages. My toddler enjoyed it too, but it’s more hands-off for that age group!
Materials:
- Large glass jar (or bowl or measuring cup)
- Paper plate or bowl large enough to cover the opening of the glass container
- Water
- Ice cubes
Procedure:
- Heat water, either in the microwave or bring to a boil on the stovetop. (I recommend that a parent take care of this step and warn little hands that the glass jar will be hot hot hot!)
- Transfer the water to your glass jar.
- Quickly, top the jar with a paper plate. Cover the plate with a pile of ice cubes.
- Watch as a mini water cycle emerges inside your glass jar!
The Science of the Water Cycle:
Rain is just one small part of the water cycle, the really awesome loop that Earth’s water has been traveling through from the ground to the sky and round and round again for billions of years. Water is never really “still”, even when it’s not actively going through the water cycle. Most of Earth’s water is stored in our oceans (roughly 96.5% of it, or 321,000,000 cubic miles) and we know the ocean is never still!
To explain the water cycle to kids, it’s easiest to break it down into four stages: evaporation, condensation, precipitation, and collection.
Evaporation
Let’s start with evaporation. That’s when the sun heats up collected water, which turns it into water vapor (a gas that we usually can’t see). This is how water begins its journey from the ground back up into the atmosphere.
There are a couple of other ways that water can leave the ground. One of those ways is sublimation, which is when solid water (ice or snow) is heated and turns directly into water vapor. This is the process you see when dry ice turns into a big cloud of water vapor, or directly from a solid into a gas, without making a pitstop and becoming a liquid.
Another way that water evaporates is through transpiration, which is basically plant sweat! Water travels from the soil, through the plant roots, and transpires (sweats) through the plants’ leaves to become water vapor and head up into the atmosphere. It’s estimated that about 10% of the water in Earth’s atmosphere is from plant transpiration.
Condensation
The next stop for all of that water vapor is condensation. As water vapor moves higher and higher into the atmosphere, it finds colder air. That colder air turns the water vapor back into a liquid.
Those cooling water molecules find tiny particles in the air (like dust, smoke, or dirt) to cling to and form cloud droplets (very, very tiny drops of condensed water), which collect and grow to form clouds (this part of the process can be called coalescence).
You see condensation all the time. When you pour a cold drink into a glass, you may see condensation form on the outside. That’s warm water vapor from the air around your glass being cooled by your drink and turning into water droplets. Your glass is kind of your own personal cloud!
Precipitation
As the cloud grows and gets heavier, we prepare for precipitation. The condensed water falls back to the ground in the form of rain, hail, snow, or sleet. This is no small task, as it takes millions of those little cloud droplets to collide and form a single rain drop.
Once a rain drop is formed, it then has to have enough velocity to make it out of the cloud and fall as precipitation! In a really heavy rainstorm, the drops are falling at a speed of 24 feet per second – that’s a little over 16 miles per hour.
There are some parts of the world where hardly any rain at all falls (less than 0.1 inches per year) and some where tons and tons of rain falls (900 inches per year). There’s a place in Chile where no rain (none!) fell for 14 years! 14! Rain is a pretty incredible thing when you stop and think about it all, right?
Collection
After the rain falls, the next stage is collection. That’s where the water settles here on Earth. Like we talked about before, about 96.5% of Earth’s water is stored in the oceans. The rest of that water (3.5%) is what we have in the atmosphere, lakes, ice caps and glaciers, rivers, streams, puddles, and everywhere else in the world! That really gives you an idea of the huge volume of water in the ocean.
And that’s the [kid friendly] water cycle!
And just like that, we are looping our way back through the water cycle. There are tons of other fun experiments and projects to learn more about it… and we will definitely revisit all of this again soon! For now, it’s time to check our rain gauge one last time and call it a [rainy] night!
One Last Thing
I’ll leave you with one last thought, sure to delight most kids. The water that you’re taking a bath in tonight could be the very same water that a dinosaur bathed in too. Rawr!
