Paper helicopter

We did a science experiment I found in the book "The Usborne Book of Science Fun." We made an easy-to-build paper helicopter (takes less than 5 minutes to make). We also made a more durable version out of art foam. Because of the way the wings stick out, the helicopter spins around as it makes its way to the ground - just let it go from a height and it does the rest. We even tried dropping it over a third floor balcony for an extra long spinning flight. A fun little experiment.

Diving pen cap

We made a pen cap that dives on command. We took a pen cap, attached a string loop around it and added four paper clips to the loop as weights. We then filled a big soda bottle with water until it was almost completely full. We dropped the pen cap into the bottle and screwed the top on tight. When we squeezed the middle of the bottle, the pen cap sank because the air bubble inside it was compressed. When we let go, the air bubble expanded again and the cap floated back to the top. It took a little practice to get the weighting and water level right. When the cap capsized, causing the air bubble to escape and the cap to sink to the bottom, we used a magnet to drag the paper clips and cap to the top so we could reach in and pull it out without emptying the bottle.

Scaredy-cat toothpicks

More fun with surface tension (one of Jr scientist A's new favorite phrases). We did an experiment showing that floating toothpicks will run in terror from soap. We arranged the toothpicks in a bowl of water so that they formed a complete enclosure - this helps them keep their relative position. You need to make sure that every toothpick, including the last one, is above another toothpick on one end and below another toothpick on the other. Then we covered the end of a new toothpick in dish detergent and gently put the soapy end into the water in the middle of the other toothpicks. Instantly the floating toothpicks moved away from the center, scattering to the edges of the bowl. A fun experiment that has a big "wow" effect, is easy to re-set up (just wash the toothpicks and bowl and refill with new water), and with a little guidance, can be a hands-on experiment for a little tyke. Now Jr. scientist A keeps asking me to do that experiment again!

Rain shadows

Even though it wasn't raining, we decided to make rain shadows. We used a spray bottle full of water as the rain. We put different objects on the dry cement and sprayed all around their edges. When we removed the objects we had a "shadow" of the object that had been there. We even made a rain shadow of Jr. scientist A. A fun experiment.

Stopping color in its tracks

This experiment was hard to pull off, but very cool once we got it to work. Since salt water is denser than fresh water, you should be able to get fresh water to sit on top of salt water, rather than all mixing together. The idea is that you put clear salt water in one container and fresh water with food coloring in another container. When you poor the colored water into the container with the salt water, the colored water should sit on top of the salt water, giving the appearance that you've stopped the color in its tracks. The only problem is that the force of pouring the colored water makes it go to the bottom of the second container before rising to the top, coloring the salt water in the process. Remembering how we got a paper clip to float using surface tension, we floated a piece of cardboard on top of the salt water and carefully poured the colored water onto the cardboard. The trick worked - although we had one attempt where some of the colored water missed the cardboard, greatly diminishing the wow factor. But when it worked, it was surreal.

Turning salt into glue

We tried to pick up ice cubes with string, using salt as the "glue." The idea is that, when you put salt on ice with the string resting on the ice, the salt lowers the ice's melting point, causing it to start to melt a little. As it refreezes, the ice freezes around the string. Our first attempt was a dud. You could feel that the string stick a little to the ice, but pulled right off. But it turned into an accidental experiment on states of matter - jr. scientist A was delighted to find that when he held the ice in his hand, it turned into water. For our second attempt, we realized that we needed to first wet the string. That turned out to be the key. With our salt and wet string, we were able to lift up the ice - although the effect was somewhat short-lived.

Rubber band-powered boat

We used a rubber band-powered boat to investigate potential and kinetic energy. The boat used popsicle sticks held together with hot glue for the body and tape-covered cardboard for the paddle. A rubber band attached to the boat body goes around the paddle. The boat is supposed to go by turning the paddle, storing energy in the rubber band, which is released when you let go of the paddle. Its maiden voyage went well, paddling slowly in the bathtub. Unfortunately, before we could try a stronger rubber band that might store more energy, the boat fell apart. I guess hot glue is not as waterproof as I thought. We'll have to try to make some other rubber band-powered toys.