Cloud in a Jar


To form a cloud in a jar and relate it to clouds forming in the atmosphere.

List of Materials:

  • Gallon jar
  • Black construction paper
  • Tape
  • Warm water
  • Plastic bag of ice that fits over jar opening
  • Matches


Tape the black construction paper on the outside of the jar. This will make the cloud easier to see. Put enough ice into a plastic bag that it won't fall through the neck of the jar. Set this aside. Next, pour the warm water into the jar. You should pour in enough that the water covers 1 to 2 inches in the bottom of the jar. Light a match and hold it just inside the top of the jar for a few seconds before dropping in into the water. Immediately, place the bag of ice on top of the jar. Watch, as the cloud forms between the water and the ice.

Water is not strange to us. It covers more than 70% of the earth's surface. The science of weather forecasting deals with water not only in the liquid state, but the invisible (vapor) and the solid (ice) states as well.

A cloud occurs when the invisible water vapor in the air becomes visible water droplets or ice crystals. The water vapor becomes visible by cooling. That is what happens on a cold wintery afternoon when you see your breath. Warm air leaving your mouth cools and forms visible droplets. The same process occurs when water is boiling on a stove. Warm air rising above boiling water cools to form droplets commonly called steam. Fog, a cloud in touch with the ground, occurs when water droplets form on particles near the earth's surface. There are many ways to make air rise and cool to form clouds. For instance, mountains force air upwards. The air that is forced to rise over the mountain cools and forms clouds. The second example is an approaching cold air mass which lifts the air ahead of it. A third process is heat from the sun. Air heated by the sun rises, cools, and forms clouds. Heat from the sun can provide enough lifting to produce a thunderstorm.

As water droplets form, they remain suspended in the atmosphere by hanging onto tiny particles also suspended in the air such as dust, pollution, ash from volcanoes or even salt particles from the sea. Because these particles are tiny and light-weight, they remain suspended in the air.

Clouds come in many different shapes. There are four major types. Cumulus are white, puffy, fair weather clouds common on a warm summer afternoon. Cumulus clouds form when air, heated by the sun, rises and cools like bubbles rising in an aquarium. If conditions are right, a cumulus cloud can grow into the cumulonimbus, a towering thunderstorm. The third type is stratus, a grey sheet-like cloud layer that blankets the sky. Finally, one easily identifies cirrus as thin feather-like clouds made of ice crystals high in the cold atmosphere. Sunlight reflecting through cirrus ice crystals can form optical phenomena around the sun or moon such as sun dogs and halos.

Key Questions:

1. What are the elements that make up the earth's weather?

2. What are the three kinds of clouds?

3. What are some weather elements associated with cloud types?

Optional Procedure:

1. Begin by having students pretend they are hiking along a mountain ridge. It's been sunny and warm all day, but you see a dark line of clouds moving from the west. Do you think this means a storm is coming? Explain that when clouds become darker, bigger, and thicker, this usually means a storm is coming. Tell them it might help to know the kinds of clouds. Begin by taking students outside with pads and pencils and having them safely observe how the clouds move. (INSTRUCT YOUR STUDENTS NEVER TO LOOK DIRECTLY AT THE SUN) If there are individual cumulus clouds, students can watch them also change shape. Have students sketch what they see.

2. Return to the classroom and discuss the various student cloud sketches. Have students use the internet and other sources to try to match their cloud sketches with those represented. You may post a cloud chart in the classroom (or make a transparency of the different cloud types from the chart). Also, you might reference for cloud pictures:

3. Discuss what process(es) led to cloud formation. Demonstrate the experiment. Why was smoke from the match important to cloud formation? (It provides particles for vapor to grab onto). Discuss that normally the sun heats the air and as the air rises, it cools to form clouds.

Have student groups choose a specific cloud to draw, color, and label on a large board and hang from the ceiling on a string to make their own classroom sky.

References: is the U.S. government's official web portal to all federal, state and local government web resources and services.