4.5 Diamond & Graphite

Question 1

Diamond (4)

Answer 1

• Pure diamonds are lustrous (sparkly) and colourless. Ideal for jewellery.
• Each carbon atom forms four covalent bonds in a very rigid giant covalent structure, which makes diamond really hard. This makes diamond ideal as cutting tools.
• All those strong covalent bonds take a lot of energy to break and give diamond a very high melting point, which is another reason diamond is a good cutting tool.
• It doesn’t conduct electricity because it has no free electrons or ions.

Question 2

Graphite (5)

Answer 2

• Graphite is black and opaque, but still kind of shiny.
• Each carbon atom only forms three covalent bonds, creating sheets of carbon atoms which are free to slide over each other.
• The layers are held together weakly so they are slippery and can be rubbed off onto paper to leave a black mark - that’s how a pencil works. This also makes graphite ideal as a lubricating material.
• Graphite’s got a high melting point - the covalent bonds need loads of energy to break.
• Since only three out of each carbon’s four outer electrons are used in bonds, there are lots of delocalised electrons that x

Question 3

What are fullerenes?

Answer 3

A fullerene is an allotrope of carbon whose molecules consist of carbon atoms connected by single and double bonds so as to form a closed or partially closed mesh, with fused rings of five to seven atoms.

Question 4

Two substances made from the same element, that are in the same physical state, but that have different structures, are called _________.

Answer 4

allotropes

Question 5

Why can diamond not conduct electricity?

Answer 5

In diamond, each carbon is bound to 4 other carbon atoms. This means there are no free electrons to carry charge, so it cannot conduct electricity.

Question 6

Unlike diamond, the carbon atoms in graphite each bond to __ other carbon atoms. This arranges the graphite into ___D layers made up of repeating _________.

Answer 6

3,2, hexagons

Question 7

Why is graphite a lot softer than diamond?

Answer 7

This is because the 2D layers of graphite stack on top of each other with only weak intermolecular forces holding them together. This means the layers can slide over each other, making graphite easier to break.

Question 8

Why is diamond brittle?

Answer 8

If the particles move suddenly, the covalent bonds will break.

Question 9

What are the two types of strength in materials?

Answer 9

• Tensile strength - how much a material can resist a pulling (stretching) force.
• Compressive strength - how much a material can resist a pushing (squashing) force.

Question 10

What are 7 different properties that materials have?

Answer 10

• Melting point
• Strength
• Stiffness
• Hardness
• Brittleness
• Ease of reshaping
• Conductivity