May 21, 2020
Test your weather knowledge
For a cloud to form, three conditions must be met. There must be water vapor, a change in temperature or pressure, and the presence small particles or condensation nuclei.
In this activity, learners will create their own clouds as they test what they know about weather and cloud formation. Using basic supplies found around your household, budding meteorologists can experiment with high and low pressure to make their very own cloud appear – and disappear!
This activity will take about 5 minutes of preparation and includes approximately 15 minutes of learning. It is best suited for elementary school children or older, but requires adult supervision no matter the learner’s age.
- 2-liter bottle with cap (all labels removed)
- Pitcher or container of water
- Fill your 2-liter bottle one-third to one-half full of water.
- Put the cap on and lightly shake the bottle so you are evaporating some of the water into the air within the bottle. Loosen the cap when you are finished shaking but leave it on the bottle.
- Ask an adult to light a match. (Make sure you are not directly under a smoke alarm.)
- Remove the cap from the bottle and have an adult slowly put the lit match into the two-liter bottle. Once the match goes out and begins to smoke, drop it into the bottle and quickly cap the bottle tightly.
- Now, repeatedly squeeze your bottle tight and release. Squeezing the bottle creates higher pressure and raises the temperature. When you release the bottle, the pressure lowers and the temperature drops, which allows the water vapor inside the bottle to condense on the smoke particles, or condensation nuclei, creating a cloud.
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- Do it again (and again)! Try filling the bottle with different amounts of water while trapping as much smoke as possible. Does this create a thicker cloud?
How to adjust for younger and older learners
For younger learners, add food coloring to the water and experiment creating the cloud with different amounts of water. Have younger learners practice pouring and measuring different amounts of water into the 2-liter bottle. Before you drop the match in the 2-liter bottle, allow your learner to blow it out first. Have your learner assist with squeezing and releasing the bottle.
For older learners, attach a bike pump to your bottle to create greater pressure and use rubbing alcohol to make a thicker cloud. You will need a bike pump with a ball-inflating needle, cork, a toothpick and safety goggles.
First create the plug using your cork making sure to fit it tight to the bottle. If the cork is longer than the needle trim it down a bit so your needle will fit all the way through. Now, insert a toothpick horizontally through the cork to prevent it from falling into the bottle when you attach the bike pump and needle.
Pour a couple ounces of rubbing alcohol into the bottle and swish it around. Put on your safety goggles, attach the pump and needle to the stopper and add several pumps of air. Once the bottle is tight, remove the stopper quickly and watch the dense cloud form! As with the previous demonstration, pumping air into the bottle increases the pressure, heating the air molecules up. When the pressure is released the molecules expand and cool. The warm air rushes out and as the cool air takes its place, these gas molecules condense into small liquid particles to form the cloud you see!