Why An Egg Floats In Salty Water?

Most of us have performed simple science experiments in elementary school. These basic activities can teach us a lot about how the world works. Making an egg float in water is one of the experiments that can show us how the salt content of water adds to an object’s ability to float.

egg-floats-in-salty-waterWith a few basic items such as a container of water, some salt and an egg, we can show that adding salt to water will allow certain solid objects to float, when common sense tells us that they shouldn’t. The simple explanation is that heavier liquids support solid objects better than lighter liquids. Adding salt to the water makes the water heavier, so it supports the egg better. In general, the water with added salt, weighs more than the egg. In a similar way, if we swim in the ocean we will have more buoyancy – we will float better than in fresh water (swimming pool, lake, etc.)

Science books explain this as a matter of density. The mass of the egg is not too large in relation to the amount of space it occupies. That’s why a rock won’t float when a piece of cork the same size will. The cork is not very dense. It doesn’t weigh much in relation to its size. The rock, however, is very dense. It weighs a lot in relation to its size.

Here’s another way to look at this subject. Getting down to the basic pieces of the puzzle, the molecules or particles in salt water are actually closer together or stick closer together than they do in fresh water. Salt water is denser and the small amount of added density from the salt makes all the difference. Trying to float an egg in the same amount of fresh water can be an exercise in frustration. If you are going to show your friends that you can make an egg float, make sure that you try it out first and know how much salt is required.

This can work for other objects too, though it will probably never work with a stone or a piece of lead. These are just too dense in relation to their size to stay on the surface.

There is one more term to be concerned with here. This helps explain why a massive ship made of steel will float in the ocean. Ocean water is very salty so it supports objects better than fresh water. The ship weighs a lot, of course! But there’s a lot of open space inside the ship and the weight is spread out so that the ship displaces a huge amount of water. Basically, an object will sink if it weighs more than the water it displaces when completely submerged!

A similar action takes place when an egg is placed in salt water. It doesn’t weigh all that much in relation to its overall size. It also weighs less than the amount of water-space it would take up if the egg was submerged.

Category: Science

9 Comments on “Why An Egg Floats In Salty Water?”


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