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Cambridge IGCSE chemistry

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  1. States of matter
    States of matter
    3 Topics
  2. Changing state
    4 Topics
  3. Diffusion
    4 Topics
  4. Atoms, elements and compounds
    Elements, compounds and mixtures
  5. Atomic structure and the Periodic Table
  6. Isotopes
  7. Ions and ionic bonds
  8. Simple molecules and covalent bonds
  9. Giant covalent structures
  10. Metallic bonding
  11. Stoichiometry
    Formulas of compounds
    3 Topics
    |
    1 Quiz
  12. Chemical equations
    5 Topics
  13. Relative atomic and molecular mass
    2 Topics
  14. Moles
    2 Topics
  15. Calculating masses in reactions
    3 Topics
  16. Percentage yield and percentage purity
    2 Topics
  17. Empirical and molecular formulae
    2 Topics
  18. Moles and concentration
    2 Topics
  19. Calculating gas volumes

Quizzes

Cambridge IGCSE chemistry Changing state Explaining changes of state (S)
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Lesson 2, Topic 3
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Explaining changes of state (S)

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Freezing and melting / boiling

  • When a solid is heated, its particles gain more energy.

  • This makes the particles vibrate more, which weakens the forces (bonds) that hold the solid together. This makes the solid expand

  • At a certain temperature, the particles have enough energy to break free from their positions. This is called melting and the solid turns into a liquid

  • When a liquid is heated, the particles get even more kinetic energy 

  • This energy makes the particles move faster, which weakens and breaks the bonds holding the liquid together

  • At a certain temperature, the particles have enough kinetic energy to break their bonds. This is called boiling and the liquid turns into a gas.

  • The amount of energy needed to cause a substance to change state depends on the strength of the forces between the particles

Heating and cooling curves

When a change of state happens energy is either released or absorbed

  • When a substance condenses or freezes the kinetic energy in its particles is converted to heat energy and released to the surroundings

  • When a substance melts or boils  heat energy is absorbed from the surroundings and converted to kinetic energy in the particles causing bonds between them to weaken or break

Heating and cooling curves are graphs showing how the temperature changes when a substance is heated or cooled at a steady rate

A-B :

  • An input of energy increases the temperature of the solid

B-C:

  • The energy is being used to reduce the attractive forces between the particles in the solid

  • So is not available to raise the temperature

C-D: 

  • The energy increases the temperature of the liquid

D-E:

  • The energy is being used to overcome the attractive forces between the particles in the liquid

  • So is not available to raise the temperature

E-F:

  • The energy increases the temperature of the gas