Have you ever made a cloud in a jar? This is a cool weather science experiment that kids of all ages will enjoy. Preschoolers will totally enjoy watching the cloud form, but I’m here to tell you that my middle school science class also loved this experiment! I had read about making a cloud in a jar several times in the past, and when this experiment showed up in our science book, my expectations were pretty low to be honest. But we were all so impressed!

The other great thing about this experiment is that it’s really easy to repeat it more than once. Kids will definitely want to watch it again, and it’s very easy to do so.

Make a cloud in a jar science

Supplies Needed:

  • A clear glass jar – it’s best if there are no ridges or words on it (not a mason jar) and no sticky label residue. Our jar was about the size of a spaghetti sauce jar.
  • Hot water from the tap
  • Matches
  • A resealable plastic bag
  • Ice
  • Black poster board or construction paper – something dark to put behind the jar to make the cloud more visible.

How to Make a Cloud in a Jar

Set up a dark background for your jar. We used a black poster board, but you can also take a piece of black paper and crease it down the middle lengthwise. Then you can stand it up behind your jar.

Then, get your baggie ready. Fill it completely with ice and close the bag.

Then, put a couple inches of hot water in the jar. Hot water from the tap is just fine! There’s no need to boil the water. If the water is too hot, it will cause a lot of condensation inside the jar, which will make it hard to see the cloud.

Next, light a match. (Adult job!!) Hold the match inside the mouth of the jar for a second, and then blow it out and drop it into the water.

Quickly place the baggie of ice on top of the jar.

The ice creates a temperature difference between the bottom of the jar and the top. The warm air rises in the jar (because that’s what warm air does), and it cools as it nears the ice. This causes the water vapor in the air to condense.

But water needs something it can condense on. It can’t condense without a surface to cling to. This is where the match comes in! The smoke particles from the match provide something for the water molecules to condense on.

Kids will be able to see the cloud swirling around in the jar as condensation happens. It’s really fun to watch!

But wait, isn’t it just smoke in the jar?

Yes, there will be smoke in the jar after you blow out the match. And smoke is NOT the same thing as water vapor, which means that it’s not the same thing as a cloud. But you’ll be able to clearly see the condensation increasing! The cloud inside the jar will visibly thicken.

Then you can remove the baggie and watch the cloud escape! So cool.

How does a cloud in a jar relate to real weather?

Clouds really do form when warm air rises, cools at higher levels of the atmosphere, and then the water vapor in the air condenses. Our cloud in a jar condensed on particles of smoke, but real clouds condense on particles of dust in the air. Pretty cool, huh?

Need more science experiments? We’ve got tons of projects that use simple supplies from around the house!

See them here: 30+ Simple Science Experiments for Kids


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  1. Linda Aug 18, 2022

    Our house is on a hill and we often have fog. Sometimes we are in it, and sometimes we are above it and can look down on the cloud, down hill in the back yard. The cloud in a jar was a great demonstration to illustrate what is happening when a cloud forms. We loved it! Thank you!


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