By Sara Thompson
Special to the Enterprise
Image reference Science Buddies, scientificamerican.com
Clouds form when water vapor in the air begins to condense. This happens when the air is over saturated with water vapor or when the air cools and goes beyond its due point. Just like condensation on the ground, the water vapor needs something to condense on. Clouds are formed when the water vapor condenses around dust particles in the air. There are a couple of different ways you can make a cloud in a jar at home.
For the first method you need a glass jar with a lid, hot water, ice cubes, and hairspray. Begin by heating about 1/3 cup of water, you want it hot but not boiling. Pour the water into the jar and swirl around a little bit so the sides of the jar heat up. Place the lid of the jar, upside-down on top of the jar. Inside the “dish” of the jar lid, place several ice cubes. Let everything sit for about 30 seconds, then gently lift the lid off the jar, spray some hairspray into the jar, then quickly replace the lid with the ice still on it. A cloud should form quickly in the jar now. How does this happen? Some of the initial hot water evaporated and turned into water vapor and rose to the top of the jar. When it comes into contact with the cooler air caused by the ice in the lid, it will condense, but has nothing to cling to until the hairspray is added to the system. The particles in the hairspray give the water vapor a surface to condense onto, forming the cloud in the jar.
Another method uses a glass jar, matches, hot water, a balloon with the narrow end cut off, and a flashlight. Again, begin by heating water enough to be hot but not boiling. Add enough water to fill the jar about a half inch, or pinky finger width. Light a match and hold it near the mouth of the jar so some of the smoke enters, then drop the match in the jar or remove it to a safe location to extinguish. Quickly stretch the balloon over the mouth of the jar to cover it. Next, gently push a finger onto the balloon, pushing it slowly into the jar. You do not want the balloon to come off the sides of the jar, but just the center being pressed inwards. When you are ready, release your hand and a cloud should start to form inside the jar. You might need a flashlight to see it better. How does this happen? With this method you are changing the air pressure within the jar. Just like the first one, when you added the hot water, some of it turned to water vapor. When you pressed down onto the balloon, you increased the pressure in the jar, slightly warming the air. When you released the balloon, the pressure dropped and the temperature cooled. The cooler air caused the water vapor to condense on the smoke from the match, forming the cloud.
Which method worked better for you? Whether you did one or both, making clouds is simply causing water vapor to condense onto tiny particles in the air, both at home and in the sky.
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