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Understand How Diamond and Graphite Are Formed

Worksheet Overview

QUESTION 1 of 10

Diamond and graphite are made of the same atoms, but their properties are totally different! How does this work?

Both diamond and graphite have giant structures made of pure carbon, but they have different patterns of bonds between the carbon atoms.

 

 

The reason diamonds are good jewels is that they are so hard. This means that they don't get scratched, so they stay shiny.

 

 

The structure of diamond is a giant covalent structure. Every carbon is linked to four other carbon atoms by covalent bonds. All the bonds in the diamond structure are covalent, so every single bond is very strong- there are no weak links in the structure. There are no free electrons or ions, so diamond cannot conduct electricity.

Graphite is also made of carbon, but the arrangement of the atoms is very different.

 

This picture shows the graphite structure. There are hexagonal rings of carbon atoms, which link together to make sheets. The bonds in the sheets are covalent, so each sheet is very strong. The bonds holding the layers together are much weaker. This means that the layers can slide over each other easily. When you write with a pencil, the "lead" in the middle is actually graphite. As you write, flakes of graphite are broken off the pencil lead and stick to the paper.

 

 

The other important difference between diamond and graphite is that graphite conducts electricity, unlike diamond. Each carbon atom in graphite makes three covalent bonds in the layer. That means there is a spare, delocalised bond which sits between the layers. These can move, which allows graphite to conduct electricity.

Even though diamond and graphite are both made of carbon atoms, the way the atoms are joined together is more important in explaining why diamond and graphite behave they ways they do.

Properties of diamond and graphite

You don't need to learn these properties by heart, but you might be asked to draw conclusions and explain patterns.

 

property diamond graphite (along layers) graphite (perpendicular to layers)
density 3.5 2.1 *
absolute hardness 1500 0.5 400
electrical conductivity 10-12 250 000 300
stiffness 100 1000 35

 

* density is mass divided by volume, so it doesn't vary with direction

For example, you could be asked: "How many times harder is diamond than the maximum hardness of graphite? Explain the difference."

 

Look in the table: hardness of diamond = 1500, maximum hardness of graphite = 400

Write a word equation: ratio = hardness of diamond ÷ hardness of graphite

Substitute numbers: ratio = 1500 ÷ 400 = 3.75

Diamond is 3.75 times harder than graphite in its hardest direction.

Link the different properties to the structure: Even in its hardest direction, graphite is weakened by the layered structure. Diamond has no weak directions.

Diamond and graphite are a nice example of structure-property relationships. The key ideas are that diamond is equally strongly bonded in all directions. Graphite has strong layers, but weaker links (with electrical conduction) in the gaps between the layers.

 

Complete the gaps in this paragraph about the structure and bonding of diamond and graphite. Use the following words:

 

all

between

carbon

covalent

four

three

What are the names of these structures?

 

Structure A Structure B

 

Which form of carbon has different properties in different directions?

Fill the gaps in these sentences. Each gap is either graphite or diamond.

Match up these half sentences about the properties and uses this form of carbon.

Column A

Column B

This is a good lubricant,
because layers can break off easily.
This is a good conductor,
because there are loosely bonded electrons between...
This is good for making marks on paper,
because the layers slide over each other easily.

Use the information in this table to help you answer this question.

property diamond graphite (along layers) graphite (perpendicular to layers)
density 3.5 2.1 *
absolute hardness 1500 0.5 400
electrical conductivity 10-12 250 000 300
stiffness 100 1000 35

 

How many times harder is graphite in its hardest direction than its least hard direction?

Use the information in this table to help you answer this question.

property diamond graphite (along layers) graphite (perpendicular to layers)
density 3.5 2.1 *
absolute hardness 1500 0.5 400
electrical conductivity 10-12 250 000 300
stiffness 100 1000 35

 

How many times denser is diamond than graphite? Give your answer to two significant figures.  

Use the information in this table to help you answer this question.

property diamond graphite (along layers) graphite (perpendicular to layers)
density 3.5 2.1 *
absolute hardness 1500 0.5 400
electrical conductivity 10-12 250 000 300
stiffness 100 1000 35

Use the options to make a correct sentence about the stiffness of carbon.

Use the information in this table to help you answer this question.

property diamond graphite (along layers) graphite (perpendicular to layers)
density 3.5 2.1 *
absolute hardness 1500 0.5 400
electrical conductivity 10-12 250 000 300
stiffness 100 1000 35

Mark the sentences in this paragraph about a potential use of graphite.

Graphite has quite good conductivity in all directions.

Diamond has good conductivity in all directions.

Graphite has very good conductivity in the direction of its layers.

Graphite is a good material to make electrical circuits.

It would be good to make electrical contacts for memory sticks from graphite

Use the information in this table to help you answer this question.

property diamond graphite (along layers) graphite (perpendicular to layers)
density 3.5 2.1 *
absolute hardness 1500 0.5 400
electrical conductivity 10-12 250 000 300
stiffness 100 1000 35

When rocks get buried, they are compressed to very high pressures. Which form of carbon would you expect to be preferred at high pressures?

  • Question 1

Complete the gaps in this paragraph about the structure and bonding of diamond and graphite. Use the following words:

 

all

between

carbon

covalent

four

three

CORRECT ANSWER
EDDIE SAYS
The starting point for thinking about diamond and graphite is their structures. Only diamond has strong covalent bonds in all directions[ the properties follow from that fact.
  • Question 2

What are the names of these structures?

 

Structure A Structure B

 

CORRECT ANSWER
EDDIE SAYS
Make sure you know how to match the names and the structure diagrams. It will help you organise the rest of your ideas about this topic.
  • Question 3

Which form of carbon has different properties in different directions?

CORRECT ANSWER
graphite
EDDIE SAYS
If properties are different in different directions, they are called anisotropic. It happens in graphite, because the structure looks totally different parallel and perpendicular to the layers. The diamond structure is much more similar in different directions.
  • Question 4

Fill the gaps in these sentences. Each gap is either graphite or diamond.

CORRECT ANSWER
EDDIE SAYS
One of the main uses of diamonds is to put on the tips of saws. They are so hard that they can cut nearly all other materials.
  • Question 5

Match up these half sentences about the properties and uses this form of carbon.

CORRECT ANSWER

Column A

Column B

This is a good lubricant,
because the layers slide over eac...
This is a good conductor,
because there are loosely bonded ...
This is good for making marks on ...
because layers can break off easi...
EDDIE SAYS
This question is a little bit sneaky, because you have to recognise that the structure is graphite before you can think about the properties.
  • Question 6

Use the information in this table to help you answer this question.

property diamond graphite (along layers) graphite (perpendicular to layers)
density 3.5 2.1 *
absolute hardness 1500 0.5 400
electrical conductivity 10-12 250 000 300
stiffness 100 1000 35

 

How many times harder is graphite in its hardest direction than its least hard direction?

CORRECT ANSWER
800
EDDIE SAYS
Highest hardness = 400 (on the layers), lowest hardness = 0.5 (between the layers), so the ratio is 400 ÷ 0.5 = 800.
  • Question 7

Use the information in this table to help you answer this question.

property diamond graphite (along layers) graphite (perpendicular to layers)
density 3.5 2.1 *
absolute hardness 1500 0.5 400
electrical conductivity 10-12 250 000 300
stiffness 100 1000 35

 

How many times denser is diamond than graphite? Give your answer to two significant figures.  

CORRECT ANSWER
1.7
EDDIE SAYS
Diamond density = 3.5, graphite density = 2.1, so the ratio is 3.5 ÷ 2.1 = 1.66667. Rounding to 2 significant figures gives 1.6|6, so the 6 rounds up to 7, giving 1.7.
  • Question 8

Use the information in this table to help you answer this question.

property diamond graphite (along layers) graphite (perpendicular to layers)
density 3.5 2.1 *
absolute hardness 1500 0.5 400
electrical conductivity 10-12 250 000 300
stiffness 100 1000 35

Use the options to make a correct sentence about the stiffness of carbon.

CORRECT ANSWER
EDDIE SAYS
This result might not be what you expected. The point is that the graphite structure has lots of C-C bonds exactly in the layer, whilst the bonds in diamond wobble around more.
  • Question 9

Use the information in this table to help you answer this question.

property diamond graphite (along layers) graphite (perpendicular to layers)
density 3.5 2.1 *
absolute hardness 1500 0.5 400
electrical conductivity 10-12 250 000 300
stiffness 100 1000 35

Mark the sentences in this paragraph about a potential use of graphite.

CORRECT ANSWER
Graphite has quite good conductivity in all directions.
Graphite has very good conductivity in the direction of its layers.
Graphite is a good material to make electrical circuits.
EDDIE SAYS
It's true that graphite has good-to-very-good conductivity, depending on the direction. We don't use it for electrical contacts (like the ones on a flash memory stick) because it breaks and wears off too easily.
  • Question 10

Use the information in this table to help you answer this question.

property diamond graphite (along layers) graphite (perpendicular to layers)
density 3.5 2.1 *
absolute hardness 1500 0.5 400
electrical conductivity 10-12 250 000 300
stiffness 100 1000 35

When rocks get buried, they are compressed to very high pressures. Which form of carbon would you expect to be preferred at high pressures?

CORRECT ANSWER
diamond
EDDIE SAYS
When we squeeze things, they need to become denser, which favours diamond over graphite. Geologists can use the presence of diamonds in rocks to work out how much they have been buried and compressed in the past.
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