Science Buddies: "Ask an Expert"

My daughter is doing the "Global Conveyor Belt" project for her local science fair. Can you please explain why the procedure uses vegetable oil instead of using salt water? Thank you

This demonstration of convection requires that you add something to whatever the liquid is that will stay neutrally bouyant in the liquid - that is to say, it won't sink, it won't float and it will just sort of tag along with the liquid as the liquid moves. You need to use a liquid that's thick enough but not *too* thick. You can try it with salt water and see if it works, but I'll guess that the scientist at Purdue University that came up with this demonstration simply found that the viscosity (thickness) of oil works better than anything else you might have in your kitchen.

Howard