This liquid may look like it's boiling hot but in fact it's freezing cold. It's liquid nitrogen!

It's so cold that even the tiniest drop could freeze whatever it contacts, which is why Kate and Fearne donned protective goggles and gloves.

Watch what happens to this ordinary squash ball when it's dropped into the tank of liquid nitrogen.

After just a few second it's frozen solid. And when it's hit with a hammer, it smashes like glass!

Flowers are made up of mostly water. The water inside them freezes solid and it stays like that until they thaw out - after which they'll go back to their original state - fresh again. Very cold liquids like this are used to preserve things.

So - that's what happens to solids. But what happens when you make a gas really cold? Well, here's a balloon filled with air.

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As the balloon goes into the tank and the gas gets cold, it takes up less room, so the balloon starts to shrink. Eventually, the gas inside turns into a liquid.

And when the balloon comes out, the liquid heats up and reverts to a gaseous state. It takes up more room and the balloon blows up again.

The liquid in the tank is nitrogen - the very same stuff that makes up most of the air we breathe. It's been made so cold that it's turned from a gas into a liquid.

If you warm up the liquid, the nitrogen turns back into a gas and takes up much more room. Here's a great demonstration, by pouring some into a bowl of warm washing up liquid.

As the liquid nitrogen warms up, it turns back into a gas and as it expands it makes all the bubbles blow up!

This expansion can be used to make things move. Here's how... Step one - we pour liquid nitrogen into a plastic bottle.

Step two - we mount the bottle on the a wire using a straw.

Step three - we quickly push a cork into the neck, and wait. The bottle goes like a rocket. The liquid turns back into a gas, takes up more room, the pressure builds up and away it goes. Very cool stuff!

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