Why water expands when frozen, speech

Hello 5/6B, Have you ever looked at water and ice, now ask our self if one is bigger. So today I’m going to talk about why water expands when frozen, and why this is unusual. It makes a big difference to the world we live in.

Water is made up of hydrogen and oxygen bonded together. Two hydrogen atoms joined to one oxygen atom. That is completes the water compound.

When water is a liquid, like it is when it comes from a tap or is in a lake or the ocean, it looks like this.

It isn’t in a structure, the molecules all float around. When water is colder, they get closer together. They are closest together at 4 degrees Celius.

But at 0 degrees, the molecules come apart create the expanded 9%

Normally, when a liquid becomes a solid, the molecules get closer together. The colder things are, the less they vibrate and can sit closer together.

Water is different because instead, the molecules get further apart. You can see it in the illustration.

The molecules have more space between them and form a solid.



The reason water expands when frozen is this?

Oxygen has a slight negative charge and hydrogen has a slight positive charge which pulls them together.

BUT when frozen to ice, they push against each other and create more space between the molecules and the ice expands.

When molecules attract it is called hydrogen-oxygen bonds.

When you look at an iceberg you only see the expanded 9%. One reason ice floats is water is more dense than ice.

In other words ice weighs less than water and that enables the ice to float. The part of ice that sticks out of the water is the expanded part of the ice.

The thing that makes ice so different from other solids is that in most solids, atoms and molecules contract together but like I said ice atoms and molecules don’t come together as much.


If water wasn’t like this, it would be easier to boil and to freeze and our world wouldn’t be anything like it is.

Water would all freeze in winter, not just in cold climates, killing all life. We don’t just need water to survive. We need water to expand on freezing to survive. To be different from most other things, to allow life to continue as we know it.







Bibliography: http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/waterdens.html http://www.thenakedscientists.com/HTML/questions/question/2435/





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