Diamond, graphite, graphene & fullerenes – GCSE Chemistry exam questions with mark scheme

1Grade 6–75 marks

Diamond and graphite are both forms of carbon.

(a) Explain why graphite conducts electricity. [2]

(b) Explain why graphite is soft and slippery but diamond is very hard. [3]

(a) each carbon atom forms three covalent bonds / one electron per carbon atom is delocalised(1)
(a) the delocalised electrons can move through the structure (and carry charge)(1)
(b) graphite has layers (of hexagonal rings) with no covalent bonds between the layers allow weak forces between layers(1)
(b) so the layers can slide over each other(1)
(b) in diamond each carbon atom is covalently bonded to four others in a rigid giant structure (strong bonds, hard to break)(1)
Answer: (a) delocalised electrons free to move (b) layers slide (weak forces between layers); diamond each C has 4 strong covalent bonds
Examiner tip: Don’t write “intermolecular forces” for diamond — it is one giant structure, so the covalent bonds themselves must break.

2Grade 1–3Foundation5 marks

The figure shows four different structures, A, B, C and D. Each structure is made only of carbon atoms.

(a) Which structure, A, B, C or D, is diamond? [1]

(b) Name the substance shown in structure C. [1]

(d) Give one use of the type of structure shown in D. [1]

(e) Name the type of bond that joins the carbon atoms together in all four structures. [1]

(a) A(1)
(b) buckminsterfullerene allow fullerene / $\text{C}_{60}$ / buckyball ignore spelling if phonetically recognisable(1)
(c) (carbon) nanotube ignore fullerene on its own reject graphene / graphite(1)
(d) any one from: nanotechnology / electronics / (reinforcing) materials, e.g. tennis rackets, bike frames allow strengthening composites / conducting wires in electronic devices ignore 'medicine' alone(1)
(e) covalent reject ionic / metallic(1)
Answer: (a) A; (b) buckminsterfullerene ($\text{C}_{60}$); (c) carbon nanotube; (d) e.g. reinforcing materials / electronics; (e) covalent
Examiner tip: In (e) 'strong' is not the name of a bond: you must write the word covalent.

3Grade 4–5Foundation6 marks

Diamond is a form of carbon. Diamond is used to make the tips of drills that cut through rock.

(a) How many covalent bonds does each carbon atom form in diamond? [1]

(b) Explain why diamond does not conduct electricity. [2]

Explain why diamond has a very high melting point. [3]

(a) 4 / four(1)
(b) all (four) outer electrons (of each carbon atom) are used in (covalent) bonds allow each carbon is bonded to four other carbon atoms(1)
(b) so there are no delocalised electrons allow no free electrons / no charged particles that can move reject no ions to move as the only reason(1)
(c) (diamond has a) giant covalent structure allow macromolecule / lattice of atoms reject any reference to molecules or intermolecular forces in diamond for this mark(1)
(c) (has) many (strong) covalent bonds allow each carbon atom bonded to 4 others by strong bonds(1)
(c) (so) a lot of energy is needed to break the (covalent) bonds reject breaking intermolecular forces(1)
Answer: (a) 4; (b) all outer electrons used in bonding so no delocalised electrons; (c) giant covalent structure with many strong covalent bonds needing lots of energy to break
Examiner tip: Any mention of breaking 'intermolecular forces' in diamond loses marks: diamond has no separate molecules, so melting means breaking covalent bonds.

4Grade 4–56 marks

The figure shows part of the structure of graphene.

The table gives some information about graphene.

Property	Graphene
Thickness	one atom
Percentage of light that passes through	97.7%
Electrical conductivity	very high
Strength compared with steel of the same thickness	about 200 times stronger
Can be bent without breaking	yes

(a) Graphene is related to graphite. Describe how. [1]

(b) Use the figure to give the number of other carbon atoms that each carbon atom is bonded to in graphene. [1]

Give two reasons from the table why graphene is suitable. [2]

(d) Graphite is soft, but graphene is very strong.

Explain why. [2]

(a) graphene is a single layer of graphite allow one layer / sheet of graphite ignore 'made of carbon' alone(1)
(b) 3 / three(1)
(c) any two from: conducts electricity (well) / lets (most) light through or is transparent so the screen can be seen / can be bent (without breaking) or is flexible / is strong — first reason (1 mark each)(1)
(c) second reason from the list above ignore 'thin' unless linked to light passing through(1)
(d) (in graphite) the layers can slide over each other (because there are only weak forces / no covalent bonds between layers) allow graphite is soft because of weak forces between layers(1)
(d) graphene is a single layer (so nothing to slide) held together by (many) strong covalent bonds between the carbon atoms allow graphene is a giant covalent layer(1)
Answer: (a) single layer of graphite; (b) 3; (c) e.g. conducts electricity and lets light through (or bends without breaking); (d) graphite's layers slide over each other; graphene is one layer held by strong covalent bonds
Examiner tip: In (c) 'it is strong' and 'it is bendable' are separate reasons, but copying 'one atom thick' with no link to the use earns nothing.

5Grade 6–7Higher5 marks

Graphene can be made by peeling single layers from a flake of graphite.

(a) A flake of graphite is 0.067 mm thick.

The distance between the layers in graphite is 0.335 nm.

$1\text{ nm} = 1 \times 10^{-9}\text{ m}$

Calculate the number of layers in the flake of graphite.

Give your answer in standard form. [3]

(b) A sheet of graphene with an area of 1.0 m² has a mass of 0.77 mg.

Calculate the area of graphene that could be made from 1.0 g of carbon.

Give your answer to 2 significant figures. [2]

(a) correct conversion to the same units: 0.067 mm = $6.7 \times 10^{-5}$ m or 0.335 nm = $3.35 \times 10^{-7}$ mm allow $67\,000$ nm(1)
(a) $\dfrac{6.7 \times 10^{-5}}{3.35 \times 10^{-10}}$ allow correct division using their converted values(1)
(a) $2 \times 10^{5}$ allow $2.0 \times 10^{5}$ allow 200 000 for 2 marks only (not in standard form)(1)
(b) 1.0 g = 1000 mg or $\dfrac{1.0}{0.77 \times 10^{-3}}$ / $\dfrac{1000}{0.77}$(1)
(b) 1300 (m²) allow $1.3 \times 10^{3}$ allow 1298.7 / 1299 for 1 mark only (not 2 s.f.); an answer of 1.3 (m²) scores 1 mark (no unit conversion)(1)
Answer: (a) $2 \times 10^{5}$ layers; (b) 1300 m²
Examiner tip: Most lost marks come from not converting mm and nm into the same unit before dividing: write both in metres first.

6Grade 6–7Higher6 marks

The figure shows a molecule of buckminsterfullerene.

(a) The formula of buckminsterfullerene is $\text{C}_{60}$.

Calculate the relative formula mass $(M_r)$ of $\text{C}_{60}$.

Relative atomic mass $(A_r)$: C = 12 [1]

(b) One molecule of buckminsterfullerene contains 12 rings of 5 carbon atoms and 20 rings of 6 carbon atoms.

Each carbon atom is part of 3 rings.

Show that these numbers give 60 carbon atoms in the molecule. [2]

Calculate the number of covalent bonds between carbon atoms in one molecule. [2]

(d) Scientists are testing fullerenes as a way of carrying medicines into the body.

Suggest which feature of the structure of fullerenes makes this possible. [1]

(a) 720(1)
(b) total ring positions $(12 \times 5) + (20 \times 6) = 180$ allow 60 + 120(1)
(b) $180 \div 3 = 60$ (because each atom is counted in 3 rings) — must show division by 3(1)
(c) $60 \times 3 = 180$ allow correct use of 'each bond joins two atoms' stated or implied(1)
(c) $180 \div 2 = 90$ (bonds) correct answer with no working = 2 marks; 180 alone scores 1 mark(1)
(d) (fullerenes are) hollow allow cage-like / the medicine (molecule) can fit inside the molecule ignore 'small' / 'large surface area'(1)
Answer: (a) 720; (b) (12×5 + 20×6) ÷ 3 = 180 ÷ 3 = 60; (c) 90; (d) hollow (cage) structure
Examiner tip: In (c) students forget that each bond is shared between two atoms, so they give 180 instead of 90.

7Grade 6–76 marks

The table shows some properties of three solid forms of carbon, W, X and Y.

Form of carbon	Melting point	Hardness	Conducts electricity when solid?	Dissolves in methylbenzene?
W	very high	very hard	no	no
X	very high	soft	yes	no
Y	low (turns to a gas easily)	soft	no	yes

(a) Which form of carbon, W, X or Y, is graphite?

Give one reason from the table for your answer. [2]

(b) Y is made of molecules with the formula $\text{C}_{60}$. Name Y. [1]

Answer in terms of structure and bonding. [3]

(a) X(1)
(a) conducts electricity (when solid) allow soft and has a very high melting point (both needed) ignore 'soft' alone (mark only if X chosen)(1)
(b) buckminsterfullerene allow fullerene / buckyball(1)
(c) Y is made of (small / simple) molecules and W is a giant covalent structure(1)
(c) (to melt) Y only needs weak forces between molecules / intermolecular forces to be overcome reject covalent bonds break in Y(1)
(c) W needs many strong covalent bonds to be broken, which needs much more energy allow converse: less energy needed to overcome intermolecular forces in Y(1)
Answer: (a) X: it conducts electricity; (b) buckminsterfullerene; (c) Y is molecular, so only weak intermolecular forces are overcome; W is giant covalent, so many strong covalent bonds must be broken, needing much more energy
Examiner tip: Saying covalent bonds break when $\text{C}_{60}$ melts is a common error that loses the second mark in (c).

8Grade 8–9Higher6 marks

Aluminium is made by electrolysis at about 950 °C. The electrodes must conduct electricity and must not melt.

An engineer considers three forms of carbon for making the electrodes: diamond, graphite and buckminsterfullerene $(\text{C}_{60})$.

Evaluate the suitability of each form of carbon for making the electrodes.

Use your knowledge of the structure and bonding of each form of carbon in your answer. [6]

diamond: each carbon atom forms four covalent bonds in a giant covalent structure(1)
diamond: very high melting point because many strong covalent bonds need a lot of energy to break, so it would not melt at 950 °C(1)
diamond: all outer electrons are used in bonding, so there are no delocalised electrons and it does not conduct, so it is unsuitable(1)
graphite: each carbon atom forms three covalent bonds in layers of hexagonal rings (giant covalent structure)(1)
graphite: very high melting point (many strong covalent bonds must be broken), so it would not melt(1)
graphite: one electron per carbon atom is delocalised; delocalised electrons can move through the structure, so it conducts electricity(1)
C60: made of simple molecules with weak intermolecular forces, so low melting point / turns to gas easily; would not stay solid at 950 °C(1)
C60: no delocalised electrons that can move through the whole structure (between molecules), so it does not conduct (well)(1)
judgement: graphite is the only one of the three that is suitable because it both conducts and does not melt(1)

Level	Marks	What it looks like
Level 3	5–6	A clear, logically linked evaluation of all three forms. Structure and bonding are used to explain both melting behaviour and electrical conductivity, and a justified conclusion identifies graphite as the suitable material.
Level 2	3–4	Relevant properties are given for at least two forms, with some correct explanation in terms of structure or bonding. Links to suitability may be incomplete, or the conclusion is not fully justified.
Level 1	1–2	Simple statements about the properties or structures of one or more forms. Little or no explanation and links to the use are missing or unclear.
No relevant content	0	Nothing worthy of credit.

Answer: Graphite is the most suitable: it conducts (delocalised electrons) and has a very high melting point (giant covalent). Diamond does not melt but does not conduct (no delocalised electrons). $\text{C}_{60}$ is molecular, so it has a low melting point / sublimes and does not conduct.
Examiner tip: Top-band answers link every property to structure for all three forms and finish with a clear judgement: listing properties with no 'because' stays in Level 2.

9Grade 8–9Higher6 marks

The figure shows the layers of carbon atoms in graphite.

A scientist measured how well a crystal of graphite conducts electricity in two directions.

Direction	Electrical conductivity in arbitrary units
along the layers	$2.4 \times 10^{6}$
across the layers	$3.0 \times 10^{2}$

(a) Calculate how many times greater the conductivity is along the layers than across the layers. [2]

(b) Suggest why graphite conducts electricity much better along the layers than across the layers. [2]

Explain what graphite and metals have in common that allows them to conduct well. [2]

(a) $\dfrac{2.4 \times 10^{6}}{3.0 \times 10^{2}}$(1)
(a) 8000 allow $8 \times 10^{3}$ correct answer with no working = 2 marks(1)
(b) (each carbon atom has one) delocalised electron which can move (freely) within / along a layer allow delocalised electrons are within each layer(1)
(b) electrons cannot move easily between the layers (because there are no covalent bonds / only weak forces between layers / the layers are far apart) reject layers slide over each other as the reason(1)
(c) both have delocalised electrons allow free / sea of electrons reject free ions / moving ions(1)
(c) which can move through the structure (and transfer energy) allow carry energy through the structure(1)
Answer: (a) 8000; (b) delocalised electrons move freely within each layer but cannot easily pass between layers; (c) both have delocalised electrons that move through the structure and transfer energy
Examiner tip: In (b), 'the layers slide' explains softness, not conductivity: the answer must be about where the delocalised electrons can move.

10Grade 6–76 marks

The figure shows part of a carbon nanotube.

(a) Carbon nanotubes belong to a family of carbon molecules. Name this family. [1]

(b) The nanotube has a diameter of 1.4 nm and a length of 0.21 mm.

$1\text{ nm} = 1 \times 10^{-9}\text{ m}$ and $1\text{ mm} = 1 \times 10^{-3}\text{ m}$

Calculate the ratio of length : diameter for this nanotube.

Give your answer in the form x : 1 [3]

(i) Suggest why carbon nanotubes make the plastic stronger. [1]

(ii) Use your answer to (b) to explain why nanotubes are better than spheres of carbon atoms for reinforcing materials. [1]

(a) fullerenes allow fullerene reject graphene / polymers(1)
(b) length = $0.21 \times 10^{-3}$ m or $2.1 \times 10^{-4}$ m and diameter = $1.4 \times 10^{-9}$ m allow both converted to any one unit, e.g. length = 210 000 nm / diameter = $1.4 \times 10^{-6}$ mm(1)
(b) $\dfrac{2.1 \times 10^{-4}}{1.4 \times 10^{-9}}$(1)
(b) 150 000 : 1 allow $1.5 \times 10^{5}$ : 1 correct answer with no working = 3 marks(1)
(c)(i) (many) strong covalent bonds (between the carbon atoms in the nanotube) allow nanotubes have high tensile strength reject ionic / intermolecular bonds(1)
(c)(ii) (very high length : diameter ratio means) nanotubes are long and thin so they can stretch through / link a large length of the material allow long fibres spread the force along the material ignore 'they are bigger'(1)
Answer: (a) fullerenes; (b) 150 000 : 1; (c)(i) strong covalent bonds; (ii) long thin tubes run through and hold the material together
Examiner tip: Convert both lengths into the same unit before dividing: an answer of 0.15 means neither was converted, and 1.5 × 10⁸ or 1.5 × 10⁻⁴ means only one was.

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