Properties and Structure of Materials - Carbon

Question 1

What are allotropes?

Answer 1

Different forms of the same element.

Question 2

What are allotropes of carbon?

Answer 2

Carbon whose atoms are bonded to each other in different, specific ways to give different, specific properties.

Question 3

What are the different allotropes of carbon?

Answer 3

Diamonds, graphite and amorphous carbon.

Question 4

Why are carbon compounds abundant in nature?

Answer 4

• It can form four types of bonds: single, double and triple covalent bonds with other elements and bonds with itself.
• It also has variety of bonding modes.
• It is vital in all living systems.

Question 5

Consider the list of physical properties given below.

(i) Conductor of electricity
(ii) High melting point
(iii) Hard substance
(iv) Inert (unreactive) substance
(v) Atoms form a three dimensional network shape

Which of these properties correspond to diamond?

(a) (i), (ii) and (iv) only
(b) (ii), (iii) (iv) and (v) only
(c) (i), (iii) and (v) only
(d) (ii), (iii) and (v) only

Answer 5

B

Question 6

Consider the list of physical properties given below.

(i) Conductor of electricity
(ii) High melting point
(iii) Hard substance
(iv) Inert (unreactive) substance
(v) Atoms form a three dimensional network shape

Which of these properties correspond to graphite?

(a) (i) and (iv) only
(b) (ii) and (v) only
(c) (i), (ii) and (iv) only
(d) (i), (iii) and (v) only

Answer 6

C

Question 7

The most significant property that distinguishes fullerenes from both diamond and graphite is their
(a) electrical conductivity.
(b) size.
(c) elemental composition.
(d) strength.

Answer 7

B

Question 8

Can carbon conduct electricity?

Answer 8

Carbon itself cannot conduct electricity as it is a non-metal however, a number of its forms can.

Question 9

What are the 3 isotopes of carbon?

Answer 9

Carbon-12
Carbon-13
Carbon-14

Question 10

What is sublimation?

Answer 10

When an element changes from a solid state directly to a gas state.

Question 11

Can carbon undergo sublimation?

Answer 11

Yes, it undergoes sublimation at temperature above 3500 degrees celsius.

Question 12

List the properties of diamonds.

Answer 12

• Very hard
• Sublimes
• Brittle
• Non-conductive

Question 13

List the properties of graphite.

Answer 13

• conductive
• slippery
• soft
• greasy material

Question 14

List the properties of amorphous carbon.

Answer 14

• conductive
• non-crystalline
• cheap

Question 15

Describe the structure of diamonds.

Answer 15

Covalent network lattice, each carbon surrounded by four other carbon atoms in a tetrahedral arrangement.

Question 16

Describe the structure of graphite.

Answer 16

Covalent layer lattice, each carbon bonded to three other carbons, one delocalised electron per carbon atom.

Question 17

Describe the structure of amorphous carbon.

Answer 17

Irregular structure of carbon atoms; many varieties exist with many different, non-continuous packing arrangements.

Question 18

List some uses of diamonds.

Answer 18

• jewellery
• cutting tools
• drills

Question 19

List some uses of graphite.

Answer 19

• lubricant
• pencils
• electrodes
• reinforcing fibres

Question 20

List some uses of amorphous carbon.

Answer 20

• printing ink
• carbon black filler
• activated charcoal
• photocopying

Question 21

Describe the structure of a diamond.

Answer 21

Does not contain individual molecules, the
carbon atoms bond to each other to form a continuous three-dimensional structure.
There are no weak intermolecular forces present, only strong covalent bonds.

Question 22

What type of structure is a diamond?

Answer 22

A covalent network lattice.

Question 23

Why are diamonds hard and rigid?

Answer 23

Single covalent bonds between carbon atoms are strong bonds. The entire structure of a diamond consists of a continuous network of these bonds, making diamond very hard and rigid.

Question 24

What does diamonds being rigid mean?

Answer 24

They are brittle.

Question 25

Why is the sublimation point of diamond very high?

Answer 25

There are no small molecules in diamond, so there are no weak forces between
the atoms.There are only strong covalent bonds between carbon atoms and this
makes the sublimation point very high (about 3500°C).

Question 26

What is the sublimation point of diamond?

Answer 26

~ 3500°C.

Question 27

Why do diamonds not conduct electricity?

Answer 27

Diamond does not conduct electricity because it does not contain any charged
particles that are free to move.

Question 28

Why is diamonds thermal conductivity very high?

Answer 28

Because the atoms in diamonds are held together very strongly, the thermal
conductivity is extremely high.

Question 29

Describe the structure of graphite.

Answer 29

The carbon atoms in graphite are in layers.There are strong covalent bonds between the carbon atoms in each layer. However, there are weak forces, called dispersion forces, between the layers.

Question 30

What type of structure is graphite?

Answer 30

Covalent layer lattice.

Question 31

Why is the sublimation point of graphite very high?

Answer 31

The strong covalent bonds between the atoms in each layer explain graphite’s resistance to heat. Graphite sublimes at a temperature of about 3600°C.

Question 32

What is the sublimation point of graphite?

Answer 32

3600°C.

Question 33

Why can graphite conduct electricity?

Answer 33

Each carbon atom is bonded to three other carbon atoms. The fourth valence electron from each atom is able to move within the layer. The electrical conductivity of graphite is due to these delocalised electrons.

Question 34

Why is graphite a good lubricant?

Answer 34

The weak dispersion forces between layers allow these layers to slide over each other and to reduce the friction between moving parts, such as in locks or machinery.