To test that, the students put bits sesame seeds and bits of walnuts between pieces of tissue and crushed them with a spoon. Low and behold, oil came out!
We also dyed some oil with food coloring, then tried to mix it with water. Oil and water don't mix; the oil just floats on top in globs. To drive the point home, students set a piece of card stock on top of the oil/water and let it sit for about twenty seconds. The card was then placed on newsprint which absorbed the excess oil and water. Students who wanted to were then able to dye their cards in different colored water/oil mixture. This project had the potential to be really messy, but the results were beautiful and really illustrated the point that oil and water don't mix.
To wrap up the unit, the children drew four different plants that give us oil and put them in a book with an oil pitcher on the front. Nice work, guys!