COVALENT BONDING AND CARBON

Question 1

Describe the structure of nanotubes

Answer 1

Hexagonal rings of carbon atoms
Arranged in a hollow cylinder

Question 2

Explain why graphite can act as a lubricant

Answer 2

There are no covalent bonds between the layers
So there are free to slide over each other

Question 3

Describe the structure of graphite

Answer 3

Each carbon atom forms 3 covalent bonds with 3 other carbon atoms
The atoms form layers made of hexagonal rings

Question 4

Name 3 properties of diamond

Answer 4

High melting and boiling points
Does not conduct electricity
Very hard

Question 5

Explain why Diamond is hard

Answer 5

It has a giant covalent structure
It has strong covalent bonds between atoms
Which are hard to break

Question 6

Explain why polymers have high melting points relative to substances made of small molecules

Answer 6

They have much larger molecules
So stronger intermolecular forces
Which require more energy to overcome

Question 7

Describe the structure of substances consisting of small molecules

Answer 7

Small molecules made up of atoms held together by strong covalent bonds.
Weak intermolecular forces act between the molecules.

Question 8

Explain why larger molecules have higher melting and boiling points than smaller ones

Answer 8

They have stronger intermolecular forces
Which require more energy to overcome

Question 9

Describe the structure of fullerenes

Answer 9

Molecules made of rings of carbon atoms will hollow shapes

Question 10

Name the first fullerene that was discovered

Answer 10

Buckminsterfullerene

Question 11

How many bonds does each carbon atom have in diamond?

Answer 11

4

Question 12

When a substance consisting of small molecules is melted or boiled , identify the forces that are overcome

Answer 12

Intermolecular forces

Question 13

Name 3 uses of nanotubes

Answer 13

Nanotechnology, electronics and materials

Question 14

Describe what happens to electrons in covalent bonding

Answer 14

They are shared between atoms

Question 15

Explain why a Buckminsterfullerene can be used as a lubricant

Answer 15

The molecules have a spherical shape so can roll over each other

Question 16

Give 2 uses of Graphene

Answer 16

Electronics and composites

Question 17

Describe the structure of graphene

Answer 17

One layer of graphite

Question 18

Give two typical properties of substances made of small molecules

Answer 18

Low melting and boiling points
Do not conduct electricity

Question 19

Name the type of structure that is made of billions of atoms covalently bonded together

Answer 19

Giant covalent structure

Question 20

Name the three main types of substances formed from covalently bonded atoms

Answer 20

Small molecules, very large molecules, and giant covalent structures

Question 21

Explain how graphite conducts electricity, making full reference to its structure and bonding

Answer 21

Each carbon atom has three bonds only
There is therefore one delocalised electron per carbon atom
The delocalised electrons are free to carry charge through graphite

Question 22

Explain why simple molecular substances have low melting points

Answer 22

Weak intermolecular forces require little energy to overcome

Question 23

Give 3 examples of substances with a giant covalent structure

Answer 23

Diamond
Silicon dioxide
Graphite

Question 24

Define polymer

Answer 24

A very large molecule made of smaller molecules joined together

Question 25

Name the type of substances that form covalent bonds when they react together

Answer 25

Non metals