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Science · Matter and heat

States of matter and the particle model

An ice cube, a glass of water and the steam rising from a kettle are the same substance. Find out how the arrangement of particles, the space between them and their motion explain the difference between solids, liquids and gases.

  • 18 min
  • 1 simulation
  • Mini quiz

Updated:

Preview

The question

When someone peels an orange in one corner of the room, a few seconds later you can smell it at the other end. How did the smell reach you? And why can you seal the tip of a syringe and squeeze the air inside, yet when you fill the same syringe with water you can hardly push the plunger at all? What is so different inside air and water?

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Ordering

Order by the space between particles

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Prediction

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In a syringe with a sealed tip, which do you think is easier to compress: air or water?

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Frequently asked

5 questions

How does the particle model explain solids, liquids and gases?

In a solid the particles are packed closely in a regular pattern and vibrate in place; a solid has a fixed shape and volume. In a liquid the particles are close together but can slide past each other; the volume is fixed but the shape follows the container. In a gas there are large gaps between the particles, which move fast and randomly; a gas fills its container.

Do particles get bigger when a substance is heated?

No. The particles themselves do not grow, shrink or soften. When heated they move faster and the distance between them increases; that is why the substance takes up more space.

Why can gases be squashed while liquids hardly can?

There is a lot of empty space between gas particles, so pushing moves them closer together. In liquids and solids the particles are already very close, so the volume can shrink only very slightly.

Do the particles in a solid not move at all?

They do. In a solid the particles do not change places, but they vibrate all the time where they are. As the solid gets warmer, this vibration increases.

Is the white cloud above a kettle water vapour?

Not exactly. Water vapour is a gas and is invisible. The white cloud you see is made of tiny water droplets that form when the vapour condenses in the cooler air. The clear-looking part right at the spout is where the actual water vapour is.