[Keywords] Thermal Properties of Matter

Important Facts That You Must Know First!

  1. Only for pure substances that the changes of state of matter occur at a fixed temperature.
  2. Boiling and evaporation are both processes of vaporisation. However, you need to know their differences.
  3. Instead of using break the inter-molecular bond, you should use “enough energy to overcome the forces of attraction between them”. “Them” refers to the molecules.
  4. How do you define condensation? Thermal energy is given out during condensation as intermolecular bonds are formed.
  5. When a substance has lower specific heat capacity, the substance is relatively more sensitive because for the same amount of heat, the increase in temperature will be more significant. This is one of the reasons why mercury is used instead of water in the thermometer.

Commonly Seen Questions

  • Explain why there is no temperature change when ice is melting and when water is boiling.
  • Explain why evaporation causes cooling.
  • Explain why increase in temperature¬† will result in faster rate of evaporation.
  • Explain why the value of specific latent heat of vaporisation of water is greater than its specific latent heat of fusion.
  • Explain how a misting fan can be used to cool the air in a room.
    • The small water droplets will evaporate gradually and remove heat from the air in the room in the process. NOTE: This method can be a double edged sword depending on the set up of the room and the context of the question. By increasing the humidity in the air, it will also lower the rate of evaporation. Furthermore, water is a poor conductor of heat but air is better at doing that job. Thus, you need to read the question carefully in order to decide from which angle that you should tackle the question.
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