Macromolecules IGCSE Grade 9 and 10

Diamond and graphite are macromolecules. Which statement about diamond and graphite is not correct?

• They are giant structures with high melting points.

• They are non-conductors of electricity.

• They contain only atoms of a non-metal.

• They have covalent bonds between the atoms.

Two statements about diamonds are given. 1 Diamond has a giant three-dimensional covalent structure of carbon atoms. 2 Diamond is one of the hardest substances known. Which is correct?

• Both statements are correct and statement 1 explains statement 2.

• Both statements are correct but statement 2 does not explain statement 1.

• Statement 1 is correct but statement 2 is incorrect.

• Statement 2 is correct but statement 1 is incorrect.

The structures of diamond and graphite are shown. Which statement about diamond and graphite is not correct?

• Diamond is used in cutting tools because the strong covalent bonds make it very hard.

• Graphite acts a lubricant because of the weak bonds between the layers.

• Graphite conducts electricity because the electrons between the layers are free to move.

• Graphite has a low melting point because of the weak bonds between the layers.

Rescuers are drilling through fallen rock in order to rescue some men trapped in a cave. The drill needs lubricating from time to time. The following statements were made about the materials used for the drill tip and the lubricant and the reasons for their use. 1Diamond was used for the drill tip as it does not conduct electricity. 2 Diamond was used for the drill tip as it is very hard. 3 Graphite was used as the lubricant as it conducts electricity. 4 Graphite was used as the lubricant as it is soft and flaky. Which statements are correct?

• 1 and 3

• 1 and 4

• 2 and 3

• 2 and 4

Graphite is a form of carbon. Why can graphite be used as a lubricant?

• Graphite contains delocalized electrons that move throughout the structure.

• Graphite contains weak covalent bonds so the atoms move easily.

• Graphite has a low melting point so it easily turns into a liquid.

• Graphite has weak forces of attraction between layers so they can move.

Slate has a layered structure and can easily be split into thin sheets. Which diagram shows a structure most like that of slate?

• A

• B

• C

• D

The ‘lead’ in a pencil is made of a mixture of graphite and clay. When the percentage of graphite is increased, the pencil slides across the paper more easily. Which statement explains this observation?

• Graphite has a high melting point.

• Graphite is a form of carbon.

• Graphite is a lubricant.

• Graphite is a non-metal.

Solid F is an element. Solid G is a compound. Neither solid conducts electricity but G conducts electricity when dissolved in water. These properties suggest that F is ……1…… and that G is ……2…… with ……3…… bonds. Which words correctly complete gaps 1, 2 and 3?

• A

• B

• C

• D

Statements 1, 2 and 3 are about diamond and graphite. 1 They are different solid forms of the same element. 2 They each conduct electricity. 3 They have atoms that form four equally strong bonds. Which statements are correct?

• 1 only

• 3 only

• 1 and 3

• 2 and 3

The diagrams show the structures of two forms, P and Q, of a solid element.

• A

• B

• C

• D