If you live in the Midwest, you know we’ve had a lot of rain the last couple weeks! Have you ever wondered what causes rain? That’s what we’re going to focus on today! You’ll create a demonstration of a rain cloud and learn how to make your own cloud in a jar!
Evaporation: Water is heated to the point that it begins to rise and turn into water vapor; when water changes from a liquid to a gas.
Condensation: Water vapor in the air is cooled, and changes from a gas back to a liquid. Examples: When you see dew on the ground in the morning, or beads of water on the outside of your water bottle.
Precipitation: When water condenses inside a cloud forming droplets so large that the cloud can’t hold them anymore. Examples: Rain, sleet, snow, hail.
First of all, what is a cloud? You may think that a cloud’s only purpose is to give us rain (or funny shapes in the sky to stare at), but they actually help regulate temperature. They reflect some of the heat from the sun back into space, so a hot day is less hot if it’s cloudy. They can also serve as a “blanket” in the evening by keeping the earth’s heat near the surface. A cool night is a little warmer if there are clouds!
Clouds are just one part of the water cycle. Think of all the places you see water in your life… make a good list.
Alright, a lot of that water you may have listed (lakes, seas, oceans, ponds) is eventually heated by the sun. When the surface of that water gets warm enough, it begins to evaporate. Once that water evaporates into the sky, it begins to cool down and condenses into clouds. If enough water vapor condenses, the droplets forming the clouds get heavier and heavier. When the drops become heavy enough, they fall as rain (or if it’s cold, they fall as snow, hail, sleet, etc.)! That rain is collected in lakes, rivers, and other bodies of water that eventually flow back to the ocean, or soaks into the ground. Then, the cycle repeats!
Create your own raincloud:
YOU WILL NEED
- A mason jar
- Shaving cream
- Blue food coloring
- A dropper
- A cup of water
Here’s what to do!
This is a simple demonstration of a raincloud.
- Pour water into your mason jar until it is about ¾ full.
- Squirt some shaving cream on top of your jar. This is your cloud.
- Mix a cup of water with some blue food coloring. Add as much food coloring as you need to make your water a nice blue. This is your rain!
- Use the dropper to drop the blue food coloring on top of the shaving cream. Observe what happens. Soon enough, your “rain” makes it through the shaving cream and precipitates into the jar. Even though this is very simple, it is a good demonstration of how a cloud works. Clouds get heavier and heavier with water until they can’t hold it anymore. Then it rains!
- Try it again, but pay attention to how many drops it takes before it starts to “rain.”
- Experiment with making different cloud shapes. Can you mimic the shapes of a stratus? Cumulus? Nimbus? Look back at the video for reference and see how many cloud models you can make!
Now we’re going to try something a little more complicated. You’re going to make a real cloud in a jar!
YOU WILL NEED:
- 2 liter plastic bottle
- Duct tape
- Bicycle pump
- Rubbing alcohol
Here’s what to do!
- Clean out a 2 liter soda bottle.
- Open the bottle and add a few teaspoons of rubbing alcohol.
- Close the bottle and rotate it around to coat the inside of the bottle with the rubbing alcohol. Rubbing alcohol evaporates very quickly, so the rotation is helping it evaporate faster.
- Put your safety glasses on! The idea is to force air into the container with the bicycle pump. Remove the cap from the bottle and cover it with duct tape to reseal the bottle. How you seal the bottle may vary depending on your type of bicycle pump.
- Poke a small hole in the middle of your duct tape seal and place the mouth of the bicycle pump over the seal. Make sure no air can escape. If you have a needle bicycle pump, a cork may work better than duct tape.
- You may need help to hold the pump over the mouth of the bottle while you pump air into it.
- Be careful! You don’t want to pump in so much air that the bottle bursts. Try about 5-7 pumps, and then quickly remove the pump from the bottle.
- Voila! You suddenly have a cloud inside a bottle!
- Try pumping air back into the bottle again… the cloud disappears!
Explanation: In the bottle, there’s air, water vapor (always in the air) and rubbing alcohol (molecules that act as places where the water molecules can land and begin to condense. Normally dust particles in the air perform this function instead of rubbing alcohol). When you pump the air in, you’re increasing pressure and ALSO increasing temperature. When you release the pressure, there’s a sudden cooling effect. What do we know about cooling? It causes condensation! Remember, condensation is what forms clouds. That’s also why when we re-add the pressure, the cloud disappears. You’re increasing pressure and heat once again, which causes that cloud to evaporate.
Another way to create a cloud:
This experiment uses boiling water and matches, so be careful and ask an adult for help.
- Mason jar
- Boiling water
- Ice cubes
Here’s what to do!
- Fill the Mason jar about half full with boiling water.
- Place the lid back on the jar.
- Put a few ice cubes on the lid and observe. You’ll see that the water vapor begins to condense on the inside of the jar. Not a cloud! Remember our last experiment… the water vapor needs something to cling to in order to form a cloud.
- Remove the lid again. Light a match, wait about five seconds, and then blow it out. Lower the match into the jar to let some smoke travel in (you don’t need a lot).
- Replace the lid and put the ice cubes back on top.
- A cloud forms! The addition of the smoke allowed the water vapor to condense, cling to the particles of smoke in the air, and form a cloud.
BONUS: If you want to learn how to predict weather based on cloud formation, check out this video! See if you can out-predict the weather person!
Tedfloyd. 1996. Natural Water Cycle. Uploaded from Wikimedia Commons on 6/19/2016.
File used in accordance with the Creative Commons CC0 1.0 Universal Public Domain Dedication license.
Beautiful Science. 2015. The science of clouds. https://www.youtube.com/watch?v=dnL5LPil77M
Nyren, E. 2016. How to make a cloud in a jar.
ZoneA. 2017. How to predict the weather by looking at the clouds. https://www.youtube.com/watch?v=I00vcHLJXCc
Good handout about cloud types:
Funk, T. Cloud classifications and characteristics.
The Science Corner. https://www.weather.gov/media/lmk/soo/cloudchart.pdf
Jessika Toothman "How Clouds Work" 5 May 2008.
HowStuffWorks.com. <https://science.howstuffworks.com/nature/climate-weather/atmospheric/cloud.htm> 26 June 2018
Robert Lamb "How Weather Works" 19 August 2008.
<https://science.howstuffworks.com/nature/climate-weather/atmospheric/weather.htm> 25 June 2018
mathtutordvd. 2012. Cloud in a bottle.