State of Matter
All matter is made of small particles known as atoms or molecules.

Molecules are small particles of matter made up of more than one atom. Water for example is made up water molecules. Each water molecule is made up of two atoms of hydrogen and one atom of oxygen.


Molecules are made up of one or more atoms.

Solids have their small particles firmly held in position. The particles (be they atoms or molecules) do not move very much but simply vibrate in position. As they gain energy, in the form of heat, they start to move and slide past each other. When this happens the substance is said to be a liquid. Now as more heat is applied the particles move very quickly and are like bullets flying through space. At this point the substance is said to be a gas. When a gas is cooled the particles lose their energy and come closer together to form a liquid. When cooled further, the particles lose most of their energy and become fixed into position and simply vibrate on the spot.

Solids are made of particles fixed in position. With heat the particles in a solid start to move around to form a liquid. Gas particles move at incredible speeds and are far apart. They bounce off the container walls and cause pressure to build up in the container.

The animation on the left shows the different stages of the water cycle. Explain the properties of the water particles as they:

-evaporate from the ocean;

-condense to form a cloud;

-form ice.

On the right is a time lapse of a drop of coloured food dye diffusing in water. The beaker on the left contains warm water while the beaker on the right contains cold water. Explain why the food dye diffuses quicker in warm water than in cold water.
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