- Density
- Miscibility
- Polarity
- Honey
- Pancake syrup
- Liquid dish soap
- Water
- Vegetable or cooking oil
- Rubbing alcohol
- Lamp oil
- A tall glass of water or other container
- (Optional) food coloring to improve visibility
*Note: for this experiment, it is not necessary to have every material listed.
- Pour the densest liquid into the glass first. Note that the liquids above are listed from most dense to least dense. Try to avoid letting the liquid run down the sides of the glass.
- Gently pour the second liquid on top of the first. One way to pour it a little more slowly is to pour the liquid over another object such as a butter knife or the back side of a spoon. Allow each layer of liquid to settle for at least a few seconds before adding the next liquid. You’ll notice that, instead of mixing, the liquids tend to stay in separate layers. The reason for this is that they are immiscible, which means that it is more thermodynamically favorable for the liquids to stay separated in layers and to form an interface than it is for them to mix together. Whether or not two liquids will be miscible is dictated by the details of the entropic and enthalpic factors associated with the mixing or separation of the two liquids in question. This is often directly related to whether or not the compounds have similar polarity. For example, we know water is a very polar substance, while vegetable oil is composed of primarily long, non-polar hydrocarbon chains. These do not interact favorably with one another, and prefer to stay in separate layers.
- Continue pouring the third, fourth, etc. liquids on top of each other in order of decreasing density (you can just follow order of your liquids in the list above). As you pour in the successive liquids, they should continue to form separate layers. The densest liquids are affected the most by gravity, so these tend to stay below the less dense liquids. These liquids are not miscible, so they do not mix together to form a single solution. In truth, if you wait long enough, some of these liquids will mix together, but it will take a while.
- That’s it! You should now see a series of separate liquid layers in your container.
