Weird Science: Mixing Air

HONOLULU (HawaiiNewsNow)-The wild and crazy science is back with Dr.V from Oceanit Hawaii. Taizo learns about the science behind juice bottles at the market. Check out the video!

Dr. V Show:  Shaking with Air

Things you will need:

  • 2 identical jars
  • Water
  • Vegetable oil
  • Food coloring (optional)

The Experiment:

Fill one jar half full with water and then add a layer of oil to this jar. In the second jar, fill it ¾ of the way with water and then fill it all the way to the very top with oil. If you'd like, add some food coloring to the water in the jars before you add the oil. Cover both jars tightly with the lids and give both jars a good shaking. What do you see? Do you see any differences?

How does it work?

You should have been able to get a good mixture of oil and water in the jar with air. What about the jar with no air. Were you able to get them to mix? Because the polarities of water and oil are different, these two liquid tend to stay separate. To mix these two liquids together, you need a lot of turbulence, or large changes in the speed and direction of the flow. This turbulence breaks up the large bunches of liquid. The more violently you are able to shake the liquid, the better your liquids will mix. However, because one fluid is floating on the other, their relative density is important, or the difference in density. The density of oil is very close to the density of water but the difference in density between oil and air is large. So with no air in the jar, the relative movement of the fluids will be much smaller than the jar with the air. The viscosity, or how thick a fluid is, also affects the mixing. So thicker fluids, like water and oil will slow down the flow and reduce mixing, but air, which has a much lower viscosity, will help mix the fluids together. This is why it can be difficult to shake a full container of liquid!

Copyright HawaiiNewsNow 2011