Water, ice and steam

It’s a really hot day and Leon wants some ice-cold lemonade. He takes out some ice cubes from the freezer and puts them in a jug. But then he realises there are no lemons at home, so he goes out to get some. When he comes back, the ice he put into the jug... has disappeared!

Lina! Why did you take the ice out of my jug! Nobody stole your ice, Leon… Why don't you look into the jug again? There isn’t any ice in the jug, but there is water. But I didn’t pour any water in there.

Wait, did the ice turn into water? Magic! It’s not magic, Leon. Water and ice are made of the same “stuff” — water molecules. Ice is solid, while water is in liquid form.

Ice and water are in different states. When you leave ice somewhere warm, the ice starts to change its state. It turns into water — it melts! Hmm, okay… But if ice turns into water when it gets warm, does water turn into ice when it gets cold? Try it!

Take your jug and stick it in the freezer. It will take a while… And… now! You can see the water in the jug has become solid and turned into ice again - it has frozen! But there is more ice than there was water! Nice observation!

When water freezes into ice, it takes up more space - it has more volume. This is because the stuff ice and water are made of — water molecules — are arranged differently. In liquid, water molecules are closer together, and in ice they are a bit further apart. This allows ice to float on top of water, like an ice floe on the ocean surface, or ice cubes in your drink. Okay, okay, I get it.

Does anything happen to ice when it gets really hot? Let’s see. Try and put your ice into a pot and onto the stove. First the ice starts to melt and turns into water. But a few minutes later… The water bubbles!

The water is now boiling and turning into a gas. It evaporates. This gas, or steam, is lighter than liquid water and rises to the surface. This creates the bubbles you see. There is actually steam in the air around you all the time, but you normally can’t see it.

Steam is transparent. But sometimes steam carries tiny droplets of liquid water, and it looks a bit like white smoke. Like when I breathe out outside on a very cold day? Precisely! Now, let’s try one more thing.

Cover the pot with a glass lid. See how the lid fogs up at first? When the hot steam touches the lid which is much colder, the steam cools down and… Look! It's turned into water again! The drops are getting bigger and bigger, and they're falling back into the pot.

Wooow! You’re getting really good at this, Leon! When steam cools down and turns back into water, we say it condenses. So, water has three different states: it can be a solid – ice, a liquid — water, and a gas — steam. And water can change from one state to another, depending on how its temperature changes.

Hey, did you get lemons and boil water for my tea? Aw, thanks Leon! Oh, no! Now I have to start all over again!