Key Concepts
Evaporation, condensation, weather, atmosphere

Introduction

Have you ever imagined yourself falling asleep on a cloud? Did you know that if you were to sleep in a cloud, you would wake up soaking wet!? There are many different types of clouds, but one thing they have in common is that they’re all made of water (or ice). But how do clouds form, and how is it possible that water can float above us in the air? In this experiment you’ll make your own cloud in a jar, and get to test the conditions that are required to make a cloud form!  

This activity is not appropriate for use as a science fair project. Good science fair projects have a stronger focus on controlling variables, taking accurate measurements, and analyzing data. To find a science fair project that is just right for you, browse our library of over 1,200 Science Fair Project Ideas or use the Topic Selection Wizard to get a personalized project recommendation.

Background

In order to understand cloud formation, we need to understand the processes of vaporization (water going from a liquid to a gas) and condensation (water going from a gas to a liquid). If you’ve ever boiled a pot of water, you’ve seen water change from a liquid to a gas. In liquid form, water molecules are packed very close together. This proximity allows the formation of hydrogen bonds between individual water molecules, so that each water molecule is connected to the water molecules surrounding it. You can observe this by looking at a droplet of water on a flat surface. Instead of spreading out flat, the water droplet holds a rounded shape. The droplet can hold this shape due to the strength of hydrogen bonds between the individual water molecules that form the droplet. 

As you heat a pot of water, you add energy to the individual water molecules. When enough energy is added, the water molecules are able to break the bonds between them, and escape as a gas into the air. As these individual water molecules break away from the surface of the boiling water and rise above the pot, they lose energy (in the form of heat). As a result, these cooler water molecules condense into tiny water droplets, that we see as steam. 

Cloud formation follows these same basic principles. As warm air rises (carrying moisture in the form of water vapor), it expands and cools. When this happens, the water vapor condenses into its liquid form. This condensation is the same type that you’ll find on your grass or car window on a spring morning. In a cloud, the water droplets attach to tiny dust particles floating in the air. Billions of these wet dust particles create a cloud!

In this experiment you will simulate cloud formation by rapidly changing the temperature of the water in the jar. You will experiment to determine what the important factors are in cloud formation, and how different conditions could change whether clouds form in our atmosphere. 

Materials

  • Glass jar with tight-sealing lid (ex: a mason jar or pickle jar)
  • Half a cup of very hot /boiling water (option to dye the water with food coloring-this won’t change the results but will make for a slightly more interesting visual)
  • Half a cup of very cold water
  • Aerosol spray can (use something clear, for example hairspray)
  • A bowl of ice cubes
  • Permanent marker or piece of tape
  • Optional: a piece of black construction paper (this will help you visualize the cloud, but it isn’t necessary)

Preparation

  1. Pour half a cup of water into the jar and use a marker or piece of tape to mark the water level on your jar. Empty the jar.
  2. If you choose to use black construction paper, set it up against a wall or propped against a book near where you will be conducting your experiment. This paper will serve as a backdrop, but you can’t pick up the jar once you put the hot water in, so the paper should be right next to your work station.
  3. Take the lids off the jar and the aerosol spray so that they’re ready to use.
  4. If you chose to use food coloring to dye the water, drop a few drops into both the hot and cold water before starting
  5. Gather all materials and arrange them in easy reach of your work station. This experiment requires you to work quickly, so prepare by having everything ready to go before starting.

Note: An adult should be in charge of pouring the hot water into the jar, as well as placing the lid on top of the jar. Steam rising from hot water can cause serious burns, and children should be warned to stand clear and observe each step.

Procedure

The first 3 steps should be done in quick succession by an adult, while children observe from a safe distance.

  1. Carefully pour the boiling water into the jar. Notice whether the water level reaches the mark you made on the jar. If it doesn’t, pay attention to exactly where the water level is right when you pour the water into the jar. What do you notice about the water? Can you see steam rising? 
  2. Quickly spray a few full sprays from the aerosol can into the jar, then seal the jar with the lid. What happens when the spray enters the jar? Do you notice anything changing?
  3. Place the ice cubes on top of the jar lid.
  4. Take a few minutes to observe what is happening inside the jar. What do you notice? What is different about the jar after you sealed the water and spray inside? 
  5. Before opening the lid, notice whether the water level has changed since you first poured the water into the jar. Has the water level changed? What might cause a change in the water level inside the jar?
  6. Slowly and carefully loosen and lift the lid from the jar.
  7. Observe the open jar. What do you notice about the contents of the jar? What is happening inside the jar? Is anything leaving the jar? What is it?
  8. Carefully (avoiding a splash) drop a few ice cubes into the jar. 
  9. Observe the jar for a few more minutes. Did the ice cubes change what was happening inside the jar? If so, what changed? 
  10. Carefully pour out the water and rinse the jar.
  11. Repeat the experiment with the cold water by following the steps below.
  12. Carefully pour the cold water into the jar. Notice whether the water level reaches the mark you made on the jar. If it doesn’t, pay attention to exactly where the water level is right when you pour the water into the jar. What do you notice about the water? Can you see steam rising? Why don’t you see steam rising with cold water? 
  13. Quickly spray a few full sprays from the aerosol can into the jar, then seal the jar with the lid. What happens when the spray enters the jar? Do you notice anything changing?
  14. Place the ice cubes on top of the jar lid.
  15. Take a few minutes to observe what is happening inside the jar. What do you notice? What is different about the jar after you sealed the water and spray inside? What is different about this experiment, compared to when you tried it with hot water?
  16. Before opening the lid, notice whether the water level has changed since you first poured the cold water into the jar. Has the water level changed? What might cause a change in the water level inside the jar?
  17. Slowly and carefully loosen and lift the lid from the jar.
  18. Observe the open jar. What do you notice about the contents of the jar? What is happening inside the jar? Is anything leaving the jar? Why or why not?

Extra: Repeat this experiment using a different liquid (for example: juice or soda). See if there are liquids that produce different results than water. What are these results, and what do you think might account for the difference?

Extra: Repeat this experiment without using the aerosol spray. Does it still work? Why or why not?

Observations and Results

When you performed this experiment with the hot water, did you observe a cloud forming? This is what is expected. When you repeated the experiment with cold water, did you observe cloud formation? You shouldn’t have seen a cloud when you used cold water, because you need heat to generate enough water evaporation to form a visible cloud. 

In this experiment you simulated cloud formation by rapidly changing the temperature of the water in the jar. When you poured the boiling water into the jar, the boiling water produced water vapor, and as this water vapor rose to the top of the jar, it was cooled by the ice cubes resting on the lid. As a result, the water vapor quickly condensed into tiny water droplets at the top of the jar. To simulate the dust particles that cause clouds in our atmosphere, we use an aerosol spray. The tiny particles released by the spray provide a surface to collect water condensation. 

When you took the lid off the jar with the hot water, you may have noticed that your cloud remained fairly intact. Tendrils of it may have started drifting away, as the warm air in the jar began to escape into the room. However, when you dropped an ice cube into the hot water, you may have observed that your cloud started disappearing more quickly. This is because the hot water quickly cooled, so it was no longer releasing water vapor. Therefore, there was no vapor to condense and form a cloud.

More to Explore

Credits

Megan Arnett, PhD, Science Buddies

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Key Concepts
Evaporation, condensation, weather, atmosphere
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