How do you make a cloud? On her show, Head Rush, Mythbuster’s Kari Byron demonstrates how clouds are formed by making one in a bottle.
For this experiment, you can use a bicycle pump with a rubber stopper attachment, rubbing alcohol and a clear 1 liter bottle. Don’t forget goggles and some adult supervision! Steve Spangler’s Science has more:
The reason the rubbing alcohol forms a more visible cloud is because alcohol evaporates more quickly than water. Alcohol molecules have weaker bonds than water molecules, so they let go of each other more easily. Since there are more evaporated alcohol molecules in the bottle, there are also more molecules able to condense. This is why you can see the alcohol cloud more clearly than the water cloud.
Clouds on Earth form when warm air rises and its pressure is reduced. The air expands and cools, and clouds form as the temperature drops below the dew point. Invisible particles in the air in the form of pollution, smoke, dust or even tiny particles of dirt help form a nucleus on which the water molecules can attach.
From the archives: clouds and experiments.
Update: Here’s an even more simple version of the experiment! Thanks, @nicolasdickner.
Mixing physics, engineering, paper and what looks like some seriously rewarding folding, cutting and taping DIY, Andrew Gatt builds incredibly sturdy paper roller coasters out of heavy paper strips. Yes! Only paper and tape was used to make this paper roller coaster… and it almost reaches a two-story high ceiling!
I included just about every feature that I could think of when I designed this roller coaster. It has a switch, three funnels, a half pipe, track hidden inside the structural beams and columns, a jump, many spirals and loops, switchbacks, hill and valley sequences, and stairs. It’s 16’4” (4.97 meters) tall, yet its base is only 13” (33 cm) by 12.5” (31 cm). It’s free standing, so it does not lean against anything for support. It weighs 2 pounds and 10 ounces (1190 grams). Besides the cardboard base, it is made of only stiff paper and tape. Every marble takes between 90 and 115 seconds to reach the end.
Andrew has more videos of his roller coasters (one at the 2012 World Maker Faire where visitors helped built it), as well as templates for sale and a gallery of student-made projects at PaperRollerCoasters.com.
Rotating Saddle (and the science behind it) from the NatSciDemos team:
A playground ball finds stability in a saddle when the saddle is rotating at the proper speed.
Mechanical analog of a “Paul Trap” particle confinement—a ball is trapped in a time-varying quadrupole gravitational potential. A large saddle shape (attached to a plywood disk) is mounted on a multi-purpose turntable. The saddle shape is essentially a quadrupole gravitational potential. Rotation of this potential subjects the ball to an alternating repulsive and attractive potential, much like the time-varying electric quadrupole potential of a Paul Trap used in trapping single ions or electrons.
The plastic ball used here is about 25 cm in diameter and was purchased at a toy store. The saddle consists of many layers of fiberglass and was hand-made with help from Justin Georgi. The turntable is driven at about 110 rpm with a DC motor. We have observed this ball at this speed remaining stable for over 2 hours.