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Q & A: Taking the Shape of the Container

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Most recent answer: 10/22/2007
Q:
When I pour water into a kind of container,what happens and why?
- Ng Hui Ching (age 11)
Tampines North Primary School, SIngapore
A:
Ng -

To understand the answer to your question, you first have to understand a little bit about the states of matter: solids, liquids, and gases. Regular water is a liquid, but if you cool it down it will turn into a solid (ice), and if you heat it up it will turn into a gas (steam).

Solids like ice are very stiff because all of the molecules inside of them (the little tiny bits of stuff that they're made of) are stuck together very tightly. And gases like steam take up a lot of space because the molecules inside aren't stuck together at all - they just fly off in every different direction.

But liquids like water are right in the middle. The molecules of water are stuck together, but not very tightly. So a single water molecule might be stuck to another molecule at one instant but let go quickly and stick to another in the next instant. You can think of it as if all the water molecules are sliding around across and over each other all the time.

Just like anything else, when gravity pulls the water molecules downwards, they will fall. But if they're in a container, the container will keep them from spreading out completely. This is what's called 'taking the shape of the container'. People say that liquids take the shape of their containers because they are stuck together enough to not go flying off like gases but not so tightly that they stay in a stiff shape like solids do.

One other thing that's pretty cool about how liquids work is something called a 'meniscus'. If you look at some water in a glass or plastic cup, you may notice that the water sort of curls up at the edges. This is because it's very easy for water to stick to plastic or glass, pulling the water up a little bit along the edges of the container.

-Tamara

(published on 10/22/2007)

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