Lemons float in water because their density is lower than that of water. Indeed, the porous skin and trapped air inside the citrus fruit allow it to float.
The density of a citrus fruit directly depends on what it contains. Generally, it is composed mostly of water, nearly 90%, with a bit of fiber, sugars, and some vitamins. So far, nothing extraordinary. But what is interesting is its outer layer, called the rind, which is very porous and full of small pockets of air. That’s what makes all the difference in terms of buoyancy. Overall, a citrus fruit is therefore less dense than water, which helps it float easily on the surface.
The peel of citrus fruits is thick and full of small pockets of air. These pockets act like mini buoys, giving the entire fruit a density lower than that of water. In other words, it's a bit like wrapping an object in a protective layer filled with air: it floats more easily! The peels of lemons, oranges, and other citrus fruits are particularly porous and spongy, allowing them to easily trap air. That's why, when you remove the peel, you take away these mini buoys, and your fruit sinks more easily.
When you submerge a lemon in water, it displaces an amount of water equal to its own volume. This is known as Archimedes' principle, an upward force that is exactly equal to the weight of the displaced water. Since citrus fruits often have a lower density than water (due to their air-filled skin), the buoyant force is greater than their own weight. The result: they simply float. Conversely, if the object's density is greater than that of water, as is the case with citrus fruits without skin, they sink, because their weight becomes greater than the upward buoyant force.
A whole lemon, with its skin, floats better because its skin is very porous and contains many small air bubbles. This layer of air acts like a true natural life jacket, significantly reducing the lemon's overall density. When you remove the skin, you take away those pockets of air. As a result, the peeled lemon becomes denser than water and tends to sink because it loses its buoyancy advantage. It's a bit like a little integrated buoy: as long as you leave it in place, it floats by itself.
Take a transparent bowl filled with cold water and some citrus fruits like lemons, oranges, and mandarins. First, try with whole fruits: you will notice that they float easily. Then, completely remove the peel from a lemon and place it back in the water: you will see that it sinks to the bottom. You can also partially cut the peel of an orange to see how its position in the water changes depending on the amount of peel remaining. These experiments clearly show that it is mainly the air-filled peel that makes the citrus fruits float.
The peel of citrus fruits, such as lemons, contains many small pores filled with air. In fact, it is these tiny air pockets that significantly increase their ability to float.
Would you like to check at home why citrus fruits float? Try this simple experiment: place lemons, oranges, or mandarins in a container of clear water, then observe their behavior as you peel them partially or completely. A simple and fun way to discover physical principles with the family!
Citrus fruits contain essential oils in their peel. These oils are less dense than water, which enhances their buoyancy when they have not been peeled.
The unpeeled lemon floats better than a peeled lemon because its thick skin traps air, providing natural buoyancy, similar to the small floats used in fishing.
Yes, other fruits or vegetables with similar structures, such as apples, peppers, and even some squashes, also exhibit buoyancy due to their internal air pockets or low overall density.
Most citrus fruits, such as oranges, grapefruits, and lemons, float in water due to their porous skin. However, once peeled, most of them sink because their density becomes slightly higher than that of water.
The freshness of the fruit does not significantly affect its ability to float. As long as the skin is intact and filled with air pockets, a fresh or older citrus fruit will naturally float. However, an old and dry skin may slightly alter the buoyancy by reducing the internal air spaces.
According to this principle, an object floats if the buoyant force (upward force) exerted by the water exceeds or is equal to the weight of the submerged object. Since whole citrus fruits have internal air pockets that reduce their overall density and therefore their specific weight, they displace enough water to generate an upward buoyant force greater than their weight, allowing them to float.
The skin of the lemon contains small air-filled spaces that help reduce the overall density of the fruit, allowing it to float. Once peeled, the lemon loses this lightweight, air-filled material, increasing its density and causing it to sink.
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