Chemistry : Unit 1 - 1.1.3 State changes and kinetic theory

• When substances are heated,the particles absorb thermal energy which is converted into kinetic energy. This is the basis of the kinetic theory of matter.
• Heating a solid causes its particles to vibrate more and as the temperature increases,they vibrate so much that the solid expands until the structure breaks and the solid melts.
• On further heating,the now liquid substance expands more and some particles at the surface gain sufficient energy to overcome the intermolecular forces and evaporate
• When the b.p. temperature is reached, all the particles gain enough energy to escape and the liquids boils
• These changes in state can be shown on a graph called a heating curve
• Cooling down a gas has the reverse effect and this would be called a cooling curve
• These curves are used to show how changes in temperature affect changes of state
• The horizontal sections occur when there is a change of state but there is no change in temperature
• Heating curve :

  A) solid to liquid

  B) Melting

  C) Solids

  D) liquid

  E) during a state change there is no temperature change

  F) Liquid/Gas

  G) Vaporization/Evaporation

  H) Gas

  
• State changes

  A) Gas

  B) Sublimation

  C) Evaporation

  D) Condensation

  E) Desublimation

  F) Liquid

  G) Melting

  H) Freezing

  I) Solid

  J) Increasing energy

  
• Cooling Curve

  A) Condensation

  B) Gas/liquid

  C) Gas

  D) Liquid

  E) Freezing

  F) Liquid/Solid

  G) Solid