Invisible paintings

We made some invisible paintings, dipping paintbrushes into lemon juice. We tried to get them to appear by heating them in the sun, but that wasn't warm enough. Instead, we found out that putting them in the oven at 350 degrees for about 5 minutes made them show up quite well. Jr. scientist A was quite proud of his now-visible paintings and decided to put them up on the fridge (o.k., the picture above was mine, which Jr. scientist A didn't deem good enough to put on the fridge!).

Unconventional bubble maker

Once again we used pressure created by warming air. We took a frozen empty bottle (my new motto is always keep an empty bottle in the freezer) and dipped the opening in bubble mix to form a soapy film over the opening. We put the bottle down and slowly a bubble started growing out of bottle. Squeezing the bottle, we could make the bubble grow quicker - o.k., it's just from the warmth from my hands, but it looks like I'm squeezing the bubble out of the bottle. Jr. scientist A had great fun popping each bubble as it formed.

Dancing pill bottle

Following up on our rubber band-powered boat, we made a dancing pill bottle. We drilled a hole in the top of a pill bottle. Then we put a rubber band around a popsicle stick and stuck the rest of the rubber band through the hole in the cap. We wrapped the other end of the rubber band around the bottom of the bottle and put the cap on the bottle. Finally, we spun the popsicle stick around to wind up the rubber band. I was hoping we might get a little helicopter-like lift out of it, but instead, it made the bottle dance around - still pretty neat.

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.