Learning Objective To be able to: Describe the structure and properties of other structures of carbon Key Words: Structure, bonding, allotrope

Exam question Wednesday, 15 May 2019 Allotropes of Carbon Date and title in books. You need a pen, pencil & ruler. Starter Activity – 5 minutes Exam question

(F) Target 9-1 Identify the properties of giant covalent structures (F/H) Target 4-9 Describe the properties of graphene and fullerenes (H) Target 5-9 Explain the properties of graphene and fullerenes, using their structure Extension: Application of Knowledge Target 8/9 Compare and contrast the properties and uses for different allotropes of carbon Learning Outcomes

What are giant covalent structures? Boardworks GCSE Additional Science: Chemistry Giant Covalent Structures What are giant covalent structures? In some substances, such as sand, diamond and graphite, millions of atoms are joined together by covalent bonds. The bonds in these substances do not form molecules, but vast networks of atoms called giant covalent structures. Photo credit (left): Tijmen van Dobbenburgh Photo credit (middle): Kia Abell Photo credit (right): Dimitris Kritsotakis All the bonds are covalent, so giant covalent structures have very high melting and boiling points, and are usually hard.

Giant Covalent Structures Substances that consist of giant covalent structures are solids with very high melting points. All of the atoms in these structures are linked to other atoms by strong covalent bonds. These bonds must be overcome to melt or boil these substances. Diamond and graphite (forms of carbon) and silicon dioxide (silica) are examples of giant covalent structures

Graphene Graphene is a single layer of graphite and has properties that make it useful in electronics. Discovery and Uses of Graphene BBC

Are there other allotropes of carbon? Boardworks GCSE Additional Science: Chemistry Giant Covalent Structures Are there other allotropes of carbon? A third class of carbon compounds, called fullerenes, has now been discovered. Buckminsterfullerene is one type of fullerene. It contains 60 carbon atoms, each of which is bonded to three others by two single and one double bond. Carbon can also form fullerenes with different numbers of carbon atoms. C The atoms in this allotrope of carbon form a sphere, like a football. The molecules can be called ‘bucky balls’. They are large but are not classified as giant structures.

What are the uses of fullerenes? Boardworks GCSE Additional Science: Chemistry Giant Covalent Structures What are the uses of fullerenes? Some of the uses of fullerenes that scientists are currently working on include: non-stick slippery coatings for machinery, which act like miniature ball bearings cages to hold drug molecules that can be delivered directly into the body The information about the uses of fullerenes is higher tier for AQA GCSE Additional Science. molecular sieves, which traps large particles like viruses while allowing smaller, healthy particles to pass through chemical sponges to soak up toxic substances in the body.

Boardworks GCSE Additional Science: Chemistry Giant Covalent Structures Nanotubes Nanotubes are another form of fullerene. They are tubes of carbon hexagons, like sheets of graphite rolled into cylinders. Nanotubes have many useful properties, including: very high tensile strength unique electrical properties good heat conductance. Multi-walled nanotubes exist. In these, several tubes can rotate and slide within in each other, almost without friction. Teacher notes Nanotubes can be used as: semiconductors in electrical circuits industrial catalysts (the catalyst can be attached to the surface of the nanotube, and a large surface area is available) reinforce graphite in tennis rackets. Metal atoms can be attached to the outer surface of the tubes. With these properties, what might nanotubes be used for?