Cloud in a jar

They say every cloud has a silver lining. Maybe it’s time to find out.

Adult supervision required

You will need:

Matches
Glass jar
Small bag of ice
Hot water
Black paper (optional)
Sticky tape to secure the black paper around the back of the jar (optional)

What to do:

Cut a small piece of black paper and secure it around the back of the jar with sticky tape. This helps us “see” the cloud better.
Pour hot water into the jar until is 1⁄4 full.
Light a match, place it over the opening of the jar and blow it out. (this must be done by an adult).
Wait a second or two then drop the match into the water inside the jar.
Quickly place the bag of ice on top of the jar covering the opening. Make sure the ice does not go down into the jar but just across the top.
Watch as the cloud begins to form!
Lift the ice and watch the cloud come out. COOL! Now’s your chance to grab it and check whether it has a silver lining. Good luck with that!

What’s going on?

The warm water heats the layer of air that it touches. Some of the water evaporates into the air forming water vapour. The warm air containing water vapour rises, and then cools, as it comes in contact with the air cooled by the ice. When the water molecules cool, they slow down and stick together more readily. The particles of smoke act as nuclei for “bunches” of water molecules to collect on. This process is called condensation.

Clouds in the real world form in a similar way to the one created in the jam jar. As the atmosphere (air) cools, water vapour suspended in the atmosphere condenses into water droplets around condensation nuclei (tiny particles of dust, ash, pollutants, and even sea salt).

In this experiment the ice is used to cool the air, however, in the real world the main cause for cooling air is to force it to rise. As air rises it expands - because the pressure decreases through the atmosphere - and therefore cools. Eventually it may become saturated and the water vapour then condenses into tiny water droplets, similar in size to those found in fog, and forms cloud. If the temperature reaches below about -20 °C, many of the cloud droplets will have frozen so that the cloud is mainly composed of ice crystals.