Floating bubbles

This has to be one of the coolest experiments we've done. Since Jr. Scientist E loves bubbles, I've been trying to find some more bubbly experiments to do with her (although she never gets tired of watching baking sod and vinegar fizz, I sure do). I ran across a cool one where you create carbon dioxide by mixing baking soda and vinegar and then you use bubble mix and blow some bubbles into the container. Since carbon dioxide is heavier than the air inside the bubble mix bubbles, the bubbles go into the container and then come to a rest in mid-air (resting on top of the invisible carbon dioxide). The bubbles will pop if they hit the edge of the container, so you need to do this in a large container with a lot of baking soda and vinegar (ah Costco, the kitchen scientist's best friend). The effect is absolutely jaw dropping and both Jr. scientists A and E loved it.

Rafting

As a first step towards making an air- or rubber band-powered boat, we took some small pieces of corkboard and turned them into rafts (that is, we put them in a pool). Our brave gingerbread man once again sailed out to sea as Jr. scientist A made waves to get the raft to go to different ends of the pool. As for Jr. scientist E, she just giggled every time the raft sailed by her. An unexpectedly fun first step towards a bigger goal.

Paper boats

After some attempts to make floating canoes with paper and glue, which inevitably sunk when the glue dissolved, friend of the lab Arthi provided us with an origami paper boat. We sailed (and sank) our boat in the bathroom sink, much to the delight of jr scientists A and E. The experiment also turned into a surface tension experiment when our paperclip passenger stayed afloat after our boat sank. Remembering back to an old experiment, we added some dish soap and watched the paperclip plummet.

Frozen boat

Inspired by an episode of MythBusters, we made a boat out of wet scraps of paper frozen together. We sandwiched the wet paper between two tupperware containers and put it all in the freezer. After it was frozen, we popped out the boat and set it to sail on the high seas of the bathroom sink with some brave gingerbread men, much to Jr. scientist A's delight. After a few minutes, the boat thawed and came apart. We put it back between the tupperware containers to re-freeze and sail again another day.

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.

Making things sink on command

Today we played with surface tension. We dropped a loop of yarn onto a bowl of water and it floated. We then added some drops of dish detergent, breaking the surface tension, and the yarn sank to the bottom. We repeated the experiment with a few other objects. A twisty-tie floated until we added the detergent. A paperclip sank right away - oops too heavy. Paper floated, even after we added detergent, but sank to the bottom when we pushed it under water. A cork floated no matter what we did. Its buoyancy amused jr. scientist A.