Why Eggs Float in Sugar Water: The Sweet Science of Density

Drop an egg into a glass of tap water and it sinks straight to the bottom. But add enough sugar to that same water, and something magical happens—the egg rises and floats. This isn't witchcraft; it's a delicious demonstration of density in action.

The science is surprisingly simple. An egg has a density of about 1.03 grams per milliliter, slightly denser than plain water at 1.0 g/mL. That tiny difference is enough to make it sink. But when you dissolve sugar in water, you're cramming more molecules into the same space without significantly increasing the volume. More mass in the same space equals higher density.

The Sugar Solution

How much sugar does it actually take? For a standard cup of water, you'll need approximately 6 tablespoons of sugar to create a solution dense enough to float an egg. That's a seriously sweet concoction—roughly 1 to 2 cups of sugar per 500mL of water if you really want to ensure success.

Here's where it gets interesting: if you've heard of the more common salt version of this experiment, you might wonder why we need so much more sugar. The answer lies in molecular weight. A half teaspoon of table salt weighs about 10 grams, while the same volume of sugar weighs only 6.5 grams. You need roughly 1.5 to 2 times as much sugar by volume to achieve the same density increase as salt.

Floating Through History

This experiment isn't some modern classroom invention. References to floating eggs in dense solutions appear in historical cooking manuscripts, where cooks used the trick to test the strength of pickling brines and preserving liquids. If an egg floated, the solution was concentrated enough to prevent spoilage.

The principle at work here—buoyancy—is the same reason you float more easily in the ocean than in a swimming pool, and why the Dead Sea is famous for making swimmers bob like corks. Salt and mineral content increase water density, reducing the effort needed to stay afloat.

Try It Yourself

This makes for an excellent kitchen science experiment because it's visual, immediate, and requires only three ingredients: water, sugar, and an egg. For extra credit, set up three glasses side by side:

• Plain tap water (egg sinks)
• Lightly sugared water (egg hovers in the middle)
• Heavily sugared water (egg floats on top)

The middle glass demonstrates neutral buoyancy—when the densities match almost perfectly, the egg can suspend at any depth, like a submarine adjusting its ballast tanks.

Next time you're stirring sugar into your coffee, remember: you're not just sweetening your drink. You're fundamentally changing its physical properties, one dissolved crystal at a time.