Plastic sulphur, Covalent and Van Der Waals bonds

Sulphur undergoes a number of distinctive changes as it is heated up to its boiling point at 445 degrees celcius.

  • It starts off as a yellow solid. On warming ……
  • ….melts to form a runny yellow liquid at 113 degrees celcius
  • Continued heating leads to a highly viscous substance that cannot be poured from the test tube.
  • with further heating the deep red viscous form of sulphur becomes more fluid. At its boiling point, 445 degrees celcius, the molten sulphur  can be poured out of the test tube.

Boiling sulphur quenched in cold water produces a different form (allotrope) called plastic sulphur because of its elastic nature.

Different forms of the same element are called allotropes. Diamond and graphite are allotropes of the element carbon.

 Your task:

Produce a powerpoint presentation a short video or poster to explain  the changes in sulphur observed as it is heated up to its boiling point. Think about the particles that are present at each stage. What are the forces between them and how does this affect their properties (in particular viscosity) Here are some key points.

  • Covalent bonds between atoms are strong ( water doesn’t break down into hydrogen and oxygen when you heat it to make a cup of coffee before school). It takeas a lot of energy to break covalent bonds
  • The forces beween molecules are comparatively weak ( they are called Van der Waals forces)
  • Van der Waals bonds are elcctrostatic in nature. Molecules can have a permanent dipole. All molecules have  transient dipoles that are continually switching on and off
  • The cumulative effect of transient dipoles increases with molar mass (the size of molecules).

Your presentation is due in next monday.

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