Shrink the Cycle

Start learning about the water cycle by experimenting with evaporation: make a water cycle in a bag. Use a permanent marker to draw the Sun and some clouds on your sandwich bag.

Pour a little water into the bag. To help you see the water better, add a couple drops of blue food coloring to your water. Seal the bag and gently shake it to mix the water and food coloring together.

Tips & Tricks:

You don’t need much water or food coloring for this to work well. One or two drops of food coloring mixed with about an inch of water is perfect.

Tape the sealed bag to a window that gets lots of natural light.

While you wait for the energy from the heat of the sun to turn the liquid water into a gas (through a process called “evaporation”), try the next activity to learn how clouds form through condensation.

Tips & Tricks:

Check on your bag throughout the day. It may take several hours for the water vapor to begin forming droplets of water that stick to the side of the bag.

Water vapor (the gaseous form of water) is found all over our atmosphere, but water vapor on its own cannot form clouds. So how do clouds form? Grab a clear plastic bottle with a screw cap (such as a two-liter bottle or a disposable water bottle), some water, a match, and help from an adult so you can find out!

Pour a small amount of water into the bottom of your bottle – you don’t need much to make this work!

Swish the water around the bottle to move more of the liquid water into water vapor. Continue swishing the water around for about 1 minute.

With the help of an adult, strike a match and blow it out. Then quickly place it into the bottle and screw on the lid. This adds ash and smoke particles into your environment.

Tips & Tricks:

You don’t need the match to burn very long for this to work.

Squeeze the bottle to increase the pressure inside the bottle.

Fun Fact:

Greater air pressure causes the air temperature to rise (get hotter), which moves more of the liquid water into the vapor form.

Stop squeezing the bottle. A cloud will form! (If you can’t see a cloud, try adding a bit more ash or try squeezing a little harder.)

Fun Fact:

When you stopped squeezing the bottle, the air pressure inside dropped, causing the temperature to drop (get cooler). As air temperature cools, water vapor clings to ash, smoke, or dirt particles and moves into the liquid form of water, creating a cloud (this process is called “condensation”). If you didn’t have the ash and smoke inside the bottle, the cloud wouldn’t be able to form.

Water needs smoke, ash, dirt, or some other microscopic particle to form a cloud, but all clouds do not create rain or snow. To learn about precipitation and how clouds release rain, gather your final materials: a clear cup, some water, shaving cream, and liquid food coloring.

Pour water into the clear cup until it is about ¾ full.

Spray a layer of shaving cream foam on top of the water, until the cup is filled.

Tips & Tricks:

Make sure the shaving cream covers the entire surface of water, but the less shaving cream you use, the faster this will work.

Add several drops of food coloring on top of the shaving cream.

It may take a couple of minutes for the weight from the liquid food coloring to make its way through the shaving cream, but when it does you will see that colored water “rain” down. This part of the water cycle is called “precipitation”. (If you need to speed it up, try adding a few drops of water on top of the food coloring.)

Fun Fact:

When enough water molecules cling together (either in their liquid or solid forms), their weight becomes so great that the gravitational pull of the Earth pulls these water droplets down toward the Earth – in the form of rain or snow!

Remember to go back and check on your water cycle in a bag. Do you see any evaporation?