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

Hydrophobic experiment

Trying to demonstrate what it means for something to be hydrophobic, we mixed together water and oil in a small (2 Tbs) measuring cup. The result was a rather unimpressive separated mixture with one layer clear and the other label an unimpressively different slight yellow. We added some red food color to the mixture - still not an impressive difference between the two layers. We tried to dye the oil a different color and learned that whatever the food coloring is made of, it's either water of hydrophilic - at best, we could get little dots of color in the oil. We'll have to work on this one.