2. Particle matters
Solids, liquids and gases P.3 of 13 
A solid lattice
Picture 2.1 The particles in a solid are fixed to their near neighbours. They vibrate around their fixed positions.

Aerosols rely on solids, liquids and gases and the way they behave.
  • All of matter is made up of particles
  • There are forces between them
  • The particles move about
  • The hotter the substance, the more vigorously its particles move.
What’s in a solid?
The particles in a solid are held in a fixed position by bonds.

The particles vibrate about their fixed position but they are always attached to the same neighbours. As the solid gets hotter, the particles vibrate more vigorously until some of the bonds start to break. At this point, the solid begins to melt.

Surface of liquid particles
Liquid particles
Picture 2.2 The forces at the surface of a liquid hold particles back. However, some escape to form a vapour above the liquid.

Liquid particles
Close to the melting point, the arrangement of the particles is quite similar to the solid. However, the particles are not strongly bonded to their neighbours and will begin to move around in the liquid. The bonds between the particles are strong enough to make it difficult for particles to escape from the surface (picture 2.2). So a liquid stays in the bottom of a container.
Freeing particles
As you heat a liquid, its particles move faster. Some particles will move fast enough to actually escape from the surface. The more you heat it, the more particles escape.

Eventually, at the boiling point, all the particles have enough energy to escape and the liquid turns into a gas.

particles in a gas
Picture 2.3 The particles in a gas are free to fill the space available to them.

Free as a gas
Gas particles are free. They move around randomly, colliding with each other and with boundary walls. A gas will always expand to fill the container that is holding it.

If they bump into a cold wall, they will lose energy and start to bind again with other gas particles. We call this condensing – a gas often forms condensation on a cold surface.

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Question 3
Look at this paragraph with gaps in it. In each case decide on the best word to fill the gap.
A is made of particles that are bound to their nearest neighbour. It to form a , in which the particles are still bound, but more loosely. This to form a that is made of free particles.

Summary                                           Close
  • all matter is made from tiny particles
  • the particles in a solid are fixed together
  • they vibrate (more as they get hotter)
  • the particles in a liquid are free to move but not to escape from the surface
  • the particles in a gas are free to fill the space available to them