States of Matter

2.1 Describe the arrangement, movement and the relative energy of particles in each of the three states of matter: solid, liquid and gas
  • The three states of matter are solid, liquid and gas
  • Melting and freezing take place at the melting point
  • Boiling and condensing take place at the boiling point

  • They can be represented by the simple model above, particles are represented by small solid spheres
  • Gas: particles have the most energy – shown by the diagram, as the particles are the most spread apart
    • Liquid: particles have more energy than those in a solid, but less than those in a gas and solid has least energy – particles are fixed
2.2 Recall the names used for the interconversions between the three states of matter, recognising that these are physical changes: contrasted with chemical reactions that result in chemical changes
  • Physical changes – therefore involves the forces between the particles of the substances, instead of these interconversions being chemical changes
  • Particle theory can help to explain melting, boiling, freezing and condensing…
    • The amount of energy needed to change state from solid to liquid and from liquid to gas depends on the strength of the forces between the particles of the substance.
    • The nature of the particles involved depends on the type of bonding and the structure of the substance.
    • The stronger the forces between the particles the higher the melting point and boiling point of the substance.
2.3 Explain the changes in arrangement, movement and energy of particles during these interconversions

*see 2.2

2.4 Predict the physical state of a substance under specified conditions, given suitable data

*see 2.2