Oil and water don’t mix; we witness this phenomenon often, such as when we dip bread into olive oil and balsamic vinegar at our favorite Italian restaurant or try to mix our favorite salad dressing. My team and I decided to delve deeper into this concept to understand what was happening at the molecular level, watch the video linked below to see what happened!
The experimental setup was as follows; we filled one clear glass cup with oil and filled another clear glass cup with water containing pink food coloring for better visibility. We carefully placed a playing card on top of the cup filled with oil and placed it upside down on top of the cup filled with water. When we removed the card to allow the oil to pour into the water, the oil and water did not mix. The oil layer remained on top of the water with a clearly formed border indicating that the liquids did not interact. When we reversed the experiment and flipped the two cups upside down, which placed the water on top and the oil on the bottom, we observed an inversion of the two liquids, but no mixing. The water sank to the bottom, while the oil rose towards the top of the cup. This inversion is due to the difference in densities between water and oil. Water is denser than oil due to the size of the molecule and the bonds being a lot closer together. The chemical properties of oil and water do account for the liquids not mixing. Water is made of one hydrogen atom covalently bonded to two oxygen atoms making water a polar molecule due to an uneven charge distribution. This polarity makes water hydrophilic, which means water attracts other polar hydrophilic molecules. In contrast, oil is a lipid made up of carbon, hydrogen, and oxygen molecules and does not have a significant charge, making oil non-polar and therefore hydrophobic. Polar and non-polar molecules do not mix well, and hydrophobic substances don’t dissolve in water, but instead repel the water molecules.
During this process, we tried to film the experimental procedure and capture our observations live. Overall, I think our experiment was conclusive showing that oil and water don’t mix. However, I think we could have modified the procedure by carefully measuring equal volumes of oil and water. Additionally, smaller volumes of each liquid should have been used, which would have been more appropriate for the size of the cups utilized in our experiment. When we performed the experiment in reverse order we should have started the procedure from the beginning instead of trying to flip the cups which resulted in the water spilling out onto the tray. Our use of pink food coloring in the water made the visualization of the two distinct liquid layers very clear. Unfortunately, we ran out of time and we were not able to fully edit the video, so the video was submitted with a few voice-over errors. Overall, this was a fun experiment.
works cited:
“Why Don't Oil and Water Mix?” Wonderopolis, https://www.wonderopolis.org/wonder/why-dont-oil-and-water-mix. Accessed 31 August 2022.
By: Kayla Kosaka
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