NCEA Level 1 chemistry: Plastic sulphur, weak forces between molecules and strong covalent bonds between atoms that make up molecules.

There are different types of sulphur. Different forms of the same element are called allotropes.

Below 95.6 oC the main allotropic form is rhombic sulphur and above this temperature the stable allotrope is monoclinic sulphur. Sulphur melts above 113 oC. The rhombic, monoclinic and yellow runny molten forms consist of  S8 molecules. When sulphur heated up to it s boiling point at 445 oC it goes through a number of remarkable changes. These changes are influenced by the particles that are present and the forces between them. Chemists are molecular architects, they need to know what the building blocks are and how they are held together

Melting sulphur


Heating sulphur to its boiling point and producing  plastic sulphur

The Class make plastic sulphur


You are the teacher. Make your own powerpoint to explain how the experiment you have done helps your class understand that the properties of materials depend on the particles that make them up and the forces between them. 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)
  • The forces beween molecules are comparatively weak ( they are called Van der Waals forces)
  • The forces between molecules get larger as the size of the molecule increases.

Finally think about all the changes you observed as sulphur was heated up to its boiling point.

The class took  photos of their work. Chose photos from the slideshow to help illustrate your powerpoint. See Shelley about these.

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