School series 62

 Why Does Ice Float?

Take a glass of water and drop an ice cube into it. The ice floats.

But here is the curious part: ice is simply frozen water. Why doesn't it sink?

The answer lies in density.

Most substances become denser when they cool and solidify. Water behaves differently. When water freezes, its molecules arrange themselves into a more open structure, leaving tiny spaces between them.

As a result, ice occupies more space than the same amount of liquid water and becomes less dense.

And anything less dense than the liquid in which it is placed floats.

This unusual property of water is extremely important for life on Earth. Ice floats on the surface of lakes and ponds, forming a protective layer while the water below remains liquid, allowing aquatic life to survive through cold winters.

So that little ice cube floating in our glass is demonstrating one of nature's most remarkable exceptions:

Water expands when it freezes—and that makes ice float.

Why Do Ships Made of Steel Float? 

Here is another puzzle.

A small piece of steel dropped into water sinks. Yet an enormous steel ship, weighing thousands of tonnes, floats.

Why?

The answer goes back to Archimedes.

A ship is not a solid block of steel. Its huge hollow shape contains a great deal of air. Because of this shape, the ship spreads its weight over a large volume and displaces a large amount of water.

The displaced water pushes upward on the ship. This upward force is called buoyancy.

When the upward buoyant force balances the ship's weight, the ship floats.

This is why the shape of a ship matters as much as the material from which it is made.

A steel ball sinks because it is compact and displaces relatively little water.

A steel ship floats because its hollow shape allows it to displace enough water to support its enormous weight.

So the secret is not that steel floats.

It doesn't.

It is the clever design of the ship that allows steel to float.

That simple principle has enabled humanity to cross oceans in vessels weighing thousands of tonnes.

Sometimes it is not the material that matters—but the way we shape it.