How to Make an Egg Float

Some objects float and some sink, right? Well, that depends on what you're floating them in. A fresh egg sinks in plain water, but it's surprisingly easy to bring it up to the surface. All you need is a single ingredient from your kitchen.

Method 1

Method 1 of 2:

Making an Egg Float

1
Fill a tall glass with water. Leave some space at the top, but don't drop the egg in yet. Since an egg is denser than plain water, it would just sink.
- Density describes how much "stuff" (mass) is pressed into a space (volume). If you pick up two objects the same size, the one that feels heavier is denser.
2
Stir in plenty of salt. Stir about 6 tablespoons (90 milliliters) of salt into the glass of water. Keep stirring until almost all the salt dissolves. (You should see almost no salt crystals at the bottom of the glass.)
- When salt dissolves in water, it "sticks" to the water molecules, fitting between them and even pulling them closer together. This means the mass increases, but the volume stays about the same.
3
Drop in an egg. The saltwater you made is denser than the glass of plain water was. If you added enough salt, the water is now denser than the egg. Test this by gently dropping the egg into the glass of water. If the water is denser, the egg will float.
- If the egg doesn't float, add more salt. Make sure to stir until the salt is dissolved.
If you pour the tap water in gently, it will sit on top of the saltwater without mixing together. The egg is lighter than the saltwater but denser than the tap water, so it will float in the middle of the glass!^{[1]XResearch source}
Here's a more complete explanation: when table salt (chemical formula NaCl) dissolves in water, it breaks apart into two atoms: sodium (Na⁺) and chlorine (Cl^-). The + and - symbols tell you that these atoms are "ions," meaning they have an electric charge. Since the opposite ends of a water molecule also have electric charges, the ions attract the water molecules closer and form a tight connection.^{[2]XResearch source}
If adding more salt makes the mixture denser, can you keep going? Could you add so much salt that a hammer could float on the water? Think about it (or test it), then click here to see the answer.
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Method 2

Method 2 of 2:

Science Experiments

1
Test eggs as they age. Is a fresh egg denser than an old egg, or is it the other way around? Line up several glasses of water with different amounts of salt stirred in, from plain water to heavy salt water. Drop a fresh, raw egg into a glass, then move it left or right until you find the least salty water the egg can float in. Repeat this each day, using a new egg from the same carton. As the eggs get older, do they float in more glasses, or sink? Read about what happened once you've tested it.
- If you can, get your eggs directly from a farmer. Supermarket eggs are often a couple weeks old when you buy them, so it will be harder to notice the difference.^{[3]XResearch source}
Do you think boiling an egg would change its density? Set up the same experiment – a row of water with different amounts of salt – but this time, compare fresh eggs with boiled eggs. Is there a difference? Read about the results.
3
Find the minimum amount of salt to float an egg. Can you think of a way to make a glass of salt water with the same density as the egg? Here's one approach:^{[4]XTrustworthy SourceScience BuddiesExpert-sourced database of science projects, explanations, and educational materialGo to source}
- Stir ⅓ cup (80 mL) salt into 1⅔ cups (400 mL) water until it all dissolves. This is a "stock solution" you will use to make other salt water mixes.
- Fill glass number 1 with ¾ cup (180 mL) of the stock solution.
- Fill glasses 2 through 5 with ¾ cup plain water each.
- Mix ¾ cup stock solution into glass number 2. This is now half as salty as glass 1.
- Take ¾ cup from glass 2 and mix it into glass 3. Glass 3 is now half as salty as glass 2.
- Mix in ¾ cup from glass 3 into glass 4. Leave glass 5 as plain water.
- Try to float an egg in each glass. If you got close to the density of the egg, it will float in the middle of the glass, stand on the base, or bob just below the surface.
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Community Q&A

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Question
If I put the egg first, followed by salt, will it still float?
Community Answer
No, the salt must be dissolved in the solvent (water) first. Mixing will allow the creation of bonds between the sodium chloride molecules and H2O molecules. Besides, when you add the egg first, followed by the salt, the egg might crack when you're trying to mix the solution. Adding to this, the salt solution might become saturated/supersaturated.
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Answers

What happens if you keep adding salt? Eventually you won't be able to dissolve it no matter how much you stir. There's no more space left between the water molecules.
Do older eggs float more easily? As eggs age, they release water vapor and gas through tiny holes in the egg shell, losing mass (and therefore density). Eventually, an egg will float in plain water.^{[5]XResearch source}
Do boiled eggs float more easily? You probably did not notice any difference between the eggs. The inside of the boiled egg changed form, but since the volume and mass did not change, neither did the density. (Eggs may lose a little water when boiled, but this mass loss is so small it is difficult to detect.)^{[6]XResearch source}

Tips

If you are doing a science experiment, label all your glasses and write down the amount of salt and water you put in each one.
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Warnings

Wash your hands in soap and water after handling raw eggs. Salmonella bacteria can live on the shell or inside the egg.^{[7]XResearch source}
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