Hydrophobic experiment, take 2

Our last hydrophobic experiment was less than successful, although we did learn that you can't dye olive oil with food coloring. Part of the problem was one of scale - it was too difficult to see the color difference with just a small layer of oil. This time we filled a small water bottle half full with water dyed red with food coloring. We then filled the other half with olive oil and sealed the bottle. We then shook up the bottle, making the liquid one uniform color. Nearly instantly the oil, being hydrophobic, started to separate out. We checked on the bottle every 1-2 minutes, watching the water and oil slowly separate. Within about 10 minutes, the two were almost completely separated, with a yellow liquid (oil) section and a red liquid (water) section.

What I liked about this experiment:

It allows a lot of jr. scientist participating - after the raw materials are in the bottle and the bottle is sealed, they can do the rest of the experiment themselves

It's infinitely resettable - at any point the bottle can be shaken and the experiment restarted

It's robust

It works quickly

It's fun

Tin can phones

We had some empty giant coffee creamer plastic containers so we decided to make some "tin can" phones. We had made some before using paper plates, string, and popsicle sticks (wrapping the string around a popsicle stick up against the plate), with limited success. The coffee creamer containers worked much better, probably because they captured sound better and added their own funny-sounding resonance. We also figured out that we could use one of the containers as an amplifier so when we strummed the string between the two "phones" we could hear a clear note come out of each container - a good example of how the string was transporting vibration and the containers were turning those vibrations into sound (o.k., technically the ear was turning them into sound and the containers were just amplifying and modifying the vibrations). Overall I'd say it was a fun experiment that worked well.