Why Do Lemons Float and Limes Sink?

If you’re someone who typically infuses their water with fruit, you might have noticed that most of the fruit in your glass floats to the top, making a colorful, and delightful, combination. One of our staffers noticed that the lemon slices in her infused water floated to the top, while the lime slices sank. Shouldn’t both of the fruits float to the top of the glass? Looking for the quickest explanation as to why this was happening, we conducted our own experiment and asked resident RD Sarah Downs to weigh in on this phenomenon.

To test out our experiment, we ran to the local grocery store and picked up limes and lemons. We tested our fruit three different ways – whole, peeled and sliced. Each time, we noticed that the lemons floated to the top of the bowl while the limes stayed relatively close to the middle/bottom of the bowl. When we peeled and sliced the fruit, the separation just continued to grow.

What we found strangest, however, was that when we peeled the fruit the limes only continued to sink deeper in the bowl while the lemons began to sink a little bit further into the bowl, but remained close to the top. The phenomenon continued when the fruit separated further after they were sliced. We assumed this happened because the fruit was sliced, therefore making the individual pieces lighter.

Based on our observations, we wanted to know the science behind why this was happening. Why, based on our observations, were the larger fruits floating to the top while the smaller fruits were sinking to the bottom? Does it have something to do with the acidity of the fruit? The weight of the peel? Or just the overall mass? We asked Sarah Downs, RD, for an explanation.

So, why do lemons float and limes sink?

Sarah Downs, RD: “The reason limes sink and lemons float is due to density, or the mass per unit of volume. An object will float if it is less dense than the liquid it is placed in and will sink if it is denser than the liquid it is placed in. Lemons and limes both have densities that are very close to water, so you would expect that they would both float. However, limes are slightly denser than lemons, which is why they sink and lemons float.”

Intrigued? Check it out for yourself in the video below: