Invisible forces

Materials
clear tupperware
pen
string
paper clip
magnet

Results
Success

Working theory
Since magnetic fields can't be seen, if we tether a paper clip and put something between the paper clip and the magnet, the magnetic field should be more apparent.

Experiment
We tied a paper clip on a string and tied the other end to the middle of a pen. We put the pen across the top of a clear tupperware with the paper clip just touching the bottom of the tupperware. We moved a magnet around under the tupperware, dragging the paper clip around through the tupperware without it getting "stuck" to the magnet.

Baking soda and vinegar rocket

Materials
soda bottle
scissors
baking soda
vinegar

Results
Perplexing

Working theory
Combining baking soda and vinegar creates a large amount of carbon dioxide gas, causing the mixture to expand and bubble out of the container. If we can direct that pressure downward, we should be able to propel the container upwards.

Experiment
We took an empty soda bottle and used a scissors to poke a hole in the lid. We put a good amount of vinegar into the bottle and filled the cap with baking soda. After our safety goggles were on we put the cap on the bottle and shook it up (with a finger over the hole). We placed the bottle on the ground, cap side down and stood back. Although the bottle became very pressurized and a bubbly stream came shooting out of the hole, we didn't get any lift. We think that either pressure was going out of the edge of the cap, near the threads (aimed upwards) or the cap wasn't flush against the ground, causing the pressure to go out at an angle.

Paper clip trains

Materials
paper clips
refrigerator magnet

Results
Success

Working theory
Ferromagnetic items (generally those with iron) can be magnetized. By rubbing a magnet across a ferromagnetic item like a paper clip, you can temporarily magnetize the item.

Experiment
We repeatedly rubbed a refrigerator magnet along a paper clip (always in the same direction - not sure if that matters). We were then able to use the magnetized paper clip to pick up another paper clip. By rubbing the magnet along multiple paper clips, we were able to make a series of magnetized paper clips. Placing them head to tail in a line we were then able to pull the whole train of paper clips by pulling the first one. We also magnetized other objects like certain keys, finding out that we could only magnetize objects that the refrigerator magnet would stick to (i.e. those that are ferromagnetic).

Rubber band guitar

Materials
Kleenex box
rubber bands
pens

Results
Success

Working theory

Sound results from periodic (i.e. regular) vibrations. Changing the length, thickness, or tautness of a rubber band should change how it vibrates and what pitch it produces.

Experiment

We started by placing different sized rubber bands around an empty Kleenex box, strumming the part of the rubber band that was over the opening of the box (where the Kleenex come out). This created a muted and muddy sound. Thinking the rubber band was up against too much of the box, preventing sustained vibrations, we moved two pens under the rubber bands and strummed in between them, making a nice note. By changing the distance between the pens (lengthening or shortening the part of the rubber band that vibrated), we were able to systematically change the pitch we got.