(Intro)

Squeaks and I are making a tiny world with just a few plants and some soil, we're going to make a small garden that can take care of itself.  It's called a terrarium.  The kind of terrarium we're making is a closed terrarium, which means it's covered and you don't need to water it.  Plants need soil, sunlight, and water to live.  The plants in a terrarium have soil and the container is clear so sunlight gets to them, but how do plants in a closed terrarium live if they can't get water?  That's right, Squeaks.  The plants in a closed terrarium get water because of the water cycle.

When it rains outside, a lot of the water goes into puddles, rivers, lakes, and oceans.  Then, the Sun warms up some of that water and it changes into what's called water vapor.  The water we see in rivers and lakes and oceans is a liquid, but water vapor is a gas like the air we breathe.  You can't see water when it's vapor, but it's still there.  Once the liquid water changes into water vapor, it rises up into the sky.  Eventually, it gets cold in the sky and the water vapor turns back into a liquid.  The little droplets of water gather into clouds and when there's a lot of water in a cloud, it falls back to the ground as rain and then the cycle starts all over again.

The same thing is going to happen in our terrarium, but on a smaller scale.  The sun will warm up the water in the terrarium, but when it turns into water vapor, the vapor will stay inside the container.  Then, when it cools down a little, the water vapor will turn back into a liquid.  You might see the water dripping down the sides of the container as it falls back down to the soil like a tiny version of a rain shower.  Then, the cycle starts all over again.  So that's how the plants in our terrarium will get water: the water cycle.

You're right, Squeaks, we can talk about it all day, but let's get to building it so we can see it with our own eyes.  Here's what you'll need for your terrarium.  First, you'll need a clear container.  It has to be clear to let the Sun in.  We're going to use this big glass jar, but you can also use a clean two liter soda bottle or an empty fish tank or whatever you want.  You should also get some plants, of course.  You'll want to use plants that like an environment with lots of water vapor in the air; plants like ferns or mosses are good for that, and you might need to have a grownup buy these at a star.  You should get some good potting soil, too.  You'll also need some small rocks and a little bit of charcoal.  They'll help the water stay clean.  Finally, you can also get some small decorations if you want. 

Okay.  If you're using a plastic bottle, the first thing you should do is cut the top off.  Ask a grownup for help with this part.  Next, wash whatever container you're using with soap and water and then dry it with a clean towel.  Now that your container is ready, you can start constructing your tiny world.  First, you should put about 2-2.5 centimeters of little rocks at the bottom.  This helps the water drain out of the soil, so it's easier for it to turn into water vapor.  On top of that, add a layer of charcoal, about 1.5 centimeters deep.  The charcoal is optional, but if you want your terrarium to last a long time, it's a good idea, because it'll keep the water clean and clean water makes healthier plants.  Next, fill about half your container with soil, and now it's time for the plants.  Decide how you want to arrange them and dig small holes with your fingers for the plants.  Then, gently put the plants in the soil.  Spread some soil over the roots and carefully pat down the soil so the plants are secure and won't fall over.  If you have decorations for your little world, now's a good time to put those in.  And now that it looks all awesome, lightly water the plants to get the water cycle started, and now it's time to close up the terrarium.  If you're using a bottle, tape the top back on.  We have a lid, and now all we have to do is put it where there's lots of light, but it won't be directly in the sun.  Near a window would be good.  

At first, the water you put in the terrarium will be soaked up by the plant's roots and the soil, but eventually, the Sun will warm it up and turn it into water vapor.  Then, when the water vapor gets a little cooler, it'll turn back into liquid water.  That's when you'll probably see it sliding down the sides of the container to water the soil and roots again.  Keep an eye on your terrarium for the first few weeks and months as the plants adjust to their new space and water cycle.  You might need to open it up and add a little more water or move it to where there's more or less light.  Once you establish a good spot and water cycle for your little world, it'll take care of itself.  Terrariums can last for a really long time.  Squeaks and I read about one that hasn't need fresh water in more than 40 years.

Have fun planting your terrarium and creating your own water cycle and let us know how it turns out.  Ask a grownup to help you leave a comment down below or send us an email to kids@scishow.com.  Thanks, and we'll see you next time here at the fort.