1. Particles of gas
The fact that the space between the rapidly moving particles in a gas is much greater than in the other two states of matter explains why the volume of a gas is much more easily changed by conditions of temperature and pressure.
If the temperature is raised then the gas particles move faster and there is less chance of interaction between them.
The gas particles move faster and more freely and occupy a greater volume.
The opposite is true if the temperature is lowered. The particles are moving more slowly. They are more likely to interact with each other and move together to occupy a smaller volume.
2. Interpretation of a cooling curve
The way the particles in the three states are arranged and interact with each other also helps to explain the energy changes involved when a substance is heated or cooled.
1. The diagram
Details Of The Diagram
From gas through the process of condensation it turns into liquid and from liquid through the process of freezing it turns into solid
2. The process from gas to liquid
The temperature is falling. The energy of the particles decreases. The particles move more slowly and interact with each other more strongly. The particles begin to come together to form the liquid. As the ( intermolecular forces - The weak force between the particles in the state of matter ) increase between the particles, energy is given out. This results in the temperature staying constant until the gas is completely condensed to liquid.
3. The process from liquid to solid
Once the liquid is formed the temperature starts to fall again . The liquid cools. The particles in the liquid slow down and eventually the solid begins to form. The forces holding the solid together form and energy is given out. While the solid is forming this release of energy keeps the temperature constant. The temperature stays the same until freezing is complete.
The key points about the processes taking place during condensation and freezing are:
• as the particles come closer together, new forces of interaction take place
• this means that energy is given out during these changes
• therefore, the temperature remains unchanged until the liquid or solid is totally formed.