Big Questions From Little People: And Simple Answers From Great Minds by Gemma Elwin Harris

Author:Gemma Elwin Harris
Language: eng
Format: mobi, epub
Tags: Science, Philosophy, Curiosities & Wonders, Reference, General
ISBN: 9780062223227
Publisher: Ecco
Published: 2012-10-30T00:00:00+00:00

WHY IS WATER WET?

Roger Highfield

director of external affairs at the Science Museum Group

One answer is to say that when you touch a puddle of water it feels wet because your fingertips tell your brain that the sensation is ‘wet’.

Nerve impulses are sending messages from your skin to your brain all the time about the world around you. We call this your sense of touch. Your sense of touch also tells you when something is dry, hot or cold, rough or smooth. Water feels wet, which means that water is a liquid.

But water is only a liquid between zero degrees celsius and a hundred degrees celsius. At zero degrees or cooler it is solid ice. If you take ice cubes from the freezer and put them in a drink at room temperature, the ice warms and starts to melt. Melting makes them liquid again. And when water in a kettle heats up over a hundred degrees it becomes a gas called water vapour, which is invisible to our eyes. (When you see steam come out of the kettle it is actually tiny drops of liquid water that form as the hot water vapour hits the cooler air around the kettle.)

If you had a super-microscope, you would see that water is made up of little particles called molecules. Each molecule is itself made up of smaller particles called atoms. You can think of these like Lego blocks, which make up the molecules used to build all the stuff (chemicals) around you, and all the stuff in your body too.

Each water molecule consists of two atoms of hydrogen stuck to one atom of oxygen. Molecules stick to each other too but it turns out that water molecules ‘glue’ each other together with hydrogen in an unusual way. You can learn the details of this special glue when you are older. All you need to know for now is that these ‘hydrogen bonds’ hold together water molecules more tightly than other similar-sized molecules that don’t have them. That makes water weird in all kinds of ways.

Here are some of the ways water is weird:

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