Home : Structures : Changes in State
There are three states of matter that we know about: solids, liquids and
gases. Each of these states is made up of particles that move by different amounts.
All solids, liquids and gases are made of particles. The only difference between them is
how much energy the particles have. If you give the particles energy; or take energy away from them; then you can change their
If you heat up a solid - you give it some energy. This causes the particles to move more and the solid to change into a
liquid, or melt. If the liquid is heated then it may evaporate and turn into a gas.
Taking energy away from a gas (cooling it down) may cause it to turn into a liquid - or condense. Further
cooling of the liquid may cause it to turn into a solid - or freeze.
To change a solid into a gas you need to give the solid particles a lot of energy, the
particles need more energy to turn from a liquid into a gas.
If you want to make a solid warmer then you give it some heat - the
graph shown here describes this. The change from a solid to a liquid requires heat energy but the temperature doesn't rise. There
isn't an increase in temperature because the energy is all used in changing the particles from a solid to a liquid.
The same thing happens when the particles change from a liquid to a gas - at first the heat given to the liquid just causes
it to warm up. Then any more heat given does not cause the temperature to rise because it is all used to change state from liquid