OCR GCSE Chemistry A: Properties of materials (J248) – Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs – examination boards hold copyright in their own papers. Use these alongside the official past papers from your board or school.

Sub-topic C2.3 Properties of materials is the focus of this set, from OCR GCSE (9-1) Chemistry A (Gateway Science), following OCR’s Version 4.0 J248 specification (August 2026). The questions span statements C2.3a to C2.3j, mathematical outcomes CM2.3i to CM2.3vi and the dissolving tablets practical suggestion (PAG C8). Every C2.3 statement can appear on either tier, as none is Higher Tier only; Foundation candidates meet it on Paper 1 and Higher candidates on Paper 3.

Work through the study guide and revision notes before attempting these. Also see the OCR GCSE Chemistry hub, the J248 checklist to print and our diagnostics, each about 10 minutes and free.

Questions

1. State the number of covalent bonds that one carbon atom forms. [1]

2. Explain why carbon forms far more compounds than any other element. [2]

3. Use these values to answer the question.

Substance	Melting point / °C	Boiling point / °C
K	−101	−34
L	44	280
M	17	118
N	801	1413

(a) State the physical state of K and of L at 20 °C. [2] (b) Which substance is a liquid at 200 °C? [1] (c) Identify the substance with the strongest forces between its particles. Explain your choice. [2]

4. Diamond and graphite both contain only carbon atoms.

(a) Only one of these two materials could serve as an electrode. Explain, in terms of electrons, which one and why the other could not. [2] (b) Explain how this shows that atoms themselves do not have the bulk properties of a material. [2]

5. A flat drawing of a model shows carbon atoms, each joined to three others, in a single hexagonal sheet one atom thick.

(a) Name this form of carbon. [1] (b) Explain why this material conducts electricity. [2] (c) Carbon nanotubes are made of this sheet rolled into a cylinder. Suggest why nanotubes are used to reinforce the frames of racing bicycles. [2]

6. Use these values: water boils at 100 °C; sodium chloride boils above 1400 °C. A student says: “When water boils, the bonds between the hydrogen and oxygen atoms break.” Explain why the student is wrong, and why water boils at a much lower temperature than sodium chloride. [4]

7. Five materials, V to Z, are tested.

Material	Melting point / °C	Electrical conduction	Other observation
V	1700	Not as solid or liquid	Very hard
W	2852	Only when molten	Brittle
X	−95	Not as solid or liquid	Liquid at room temperature
Y	660	As solid and liquid	Can be hammered into sheets
Z	Softens from 105 to 120	Not as solid	Long-chain solid, flexible

Identify the type of structure in each material: ionic, simple molecular, giant covalent, metallic or polymer. [5]

8. A nanoparticle of a catalyst is 25 nm across. Take the diameter of one atom as 0.25 nm.

(a) Write 25 nm in metres, in standard form. [1] (b) Estimate the number of atoms that would fit side by side across the nanoparticle. [2] (c) A grain of sand is 0.5 mm across. Calculate how many times wider it is than the nanoparticle. [2]

9. A catalyst is made either as cubes of side 60 nm or as cubes of side 6 nm.

(a) Calculate the surface area, the volume and the surface area to volume ratio of one 60 nm cube. [3] (b) Calculate the surface area to volume ratio of one 6 nm cube, and state how many times larger it is than in part (a). [2] (c) Explain why the same mass of catalyst works faster as 6 nm cubes. [2]

10. A student investigates how particle size affects dissolving. She drops an effervescent tablet into 100 cm³ of water at 20 °C and times how long it takes to dissolve. Her results:

Tablet form	Trial 1 / s	Trial 2 / s	Trial 3 / s
Whole	62	65	59
Four pieces	41	44	38
Powder	18	31	20

(a) Calculate the mean time for the whole tablet and for the four pieces. [2] (b) Identify the anomalous result. [1] (c) Calculate the mean time for the powder, leaving out the anomalous result. [2] (d) Explain the trend in the results. [2]

11. A company plans to add zinc oxide nanoparticles to a clear varnish for outdoor wooden furniture. The nanoparticles absorb ultraviolet light, which otherwise damages wood. Evaluate this plan. Refer to the properties of nanoparticles, the benefits and the possible risks. [8]

Answers

1. Four [1]. [1] Examiner insight: A number on its own answers this; extra detail that is wrong risks contradicting a correct answer.

2. Carbon forms four covalent bonds, including strong bonds to other carbon atoms [1]. So it forms chains and rings of many lengths, giving families of similar compounds [1]. [2] Examiner insight: Two separate points are needed for two marks: the bonding of carbon, and the chains, rings or families that result.

3. (a) K: gas, as 20 °C is above its boiling point of −34 °C [1]. L: solid, as 20 °C is below its melting point [1]. (b) L (200 °C lies between 44 °C and 280 °C) [1]. (c) N [1]. It has the highest melting and boiling points, so the most energy is needed to overcome the forces between its particles [1]. [5] Examiner insight: With negative values, write the comparison out (for example “20 is above −34”) so the reasoning is visible and the direction cannot be misread.

4. (a) In graphite each carbon bonds to three others, leaving one delocalised electron per atom that can move through the layers [1]. Diamond’s carbons each bond to four others, so no outer electron is left free to move [1]. (b) Both contain identical carbon atoms, yet one conducts and the other does not [1], so conduction depends on how the atoms are bonded and arranged, not on the atoms themselves [1]. [4] Examiner insight: Say “delocalised electrons”; answers that call the moving particles in graphite “ions” or “atoms” describe the wrong particle.

5. (a) Graphene [1]. (b) Each carbon uses three electrons in bonds [1], so one electron per carbon is delocalised and moves across the sheet carrying charge [1]. (c) Nanotubes are very strong because of strong covalent bonds along their length [1], and they are light, so the frame gains strength without much added mass [1]. [5] Examiner insight: In “suggest” questions, link each property to the use; “strong and light” alone earns less than “strong, so the frame resists bending”.

6. Water is a simple molecular substance; boiling overcomes the weak intermolecular forces between molecules [1], and the covalent bonds inside the molecules do not break [1]. Sodium chloride is a giant ionic lattice with strong electrostatic attraction between ions [1]. Far more energy is needed to overcome these, so its boiling point is much higher [1]. [4] Examiner insight: Name the force in both substances; an answer that only says “water has weaker bonds” is too vague to gain much.

7. V: giant covalent [1]. W: ionic [1]. X: simple molecular [1]. Y: metallic [1]. Z: polymer [1]. [5] Examiner insight: Use the conduction column first: conducting as a solid points to a metal, conducting only when molten points to ionic.

8. (a) 2.5 × 10⁻⁸ m [1]. (b) 25 ÷ 0.25 [1] = 100 atoms [1]. (c) 0.5 mm = 5 × 10⁻⁴ m; 5 × 10⁻⁴ ÷ 2.5 × 10⁻⁸ [1] = 20 000 times [1]. [5] Examiner insight: Convert both sizes to the same unit before dividing, and write the conversion down so your method is clear.

9. (a) Surface area = 6 × 60² = 21 600 nm² [1]. Volume = 60³ = 216 000 nm³ [1]. Ratio = 21 600 ÷ 216 000 = 0.1 nm⁻¹ (0.1 : 1) [1]. (b) 6 × 6² ÷ 6³ = 216 ÷ 216 = 1.0 nm⁻¹ [1], which is 10 times larger [1]. (c) The same mass as 6 nm cubes has a much larger total surface area (ten times as much) [1], so more catalyst atoms are at the surface where reacting particles collide with it [1]. [7] Examiner insight: Units on area (nm²) and volume (nm³) are worth writing; a ratio with the wrong power of ten usually comes from cubing or squaring the wrong number.

10. (a) Whole: (62 + 65 + 59) ÷ 3 = 62 s [1]. Four pieces: (41 + 44 + 38) ÷ 3 = 41 s [1]. (b) 31 s (powder, trial 2) [1]. (c) (18 + 20) ÷ 2 [1] = 19 s [1]. (d) The smaller the pieces, the shorter the dissolving time [1], because smaller pieces have a larger surface area to volume ratio, so more of the tablet is in contact with water [1]. [7] Examiner insight: If you leave out an anomaly, divide by the number of values you actually used; dividing 38 by 3 is a common slip.

11. Any eight creditworthy points, including benefits, risks and a judgement:

• Zinc oxide nanoparticles absorb ultraviolet light, protecting the wood from damage [1].
• They are too small to scatter much visible light, so the varnish stays clear rather than white [1].
• Their large surface area to volume ratio means a small mass gives good coverage [1].
• Furniture lasts longer, so less wood is replaced [1].
• Risk: as varnish wears or is sanded, nanoparticles may be released and breathed in [1].
• Risk: their large surface area may make them more reactive or toxic than bulk zinc oxide [1].
• Risk: rain may wash particles into soil and water, where they could harm organisms [1].
• Judgement: long-term effects are not fully known, so the plan is reasonable only with safety testing, labelling and guidance on sanding [1]. [8]

Examiner insight: An “evaluate” answer needs both sides and a reasoned conclusion; a list of benefits with no risks, or no final judgement, limits the credit.

Where marks are usually lost

• Writing that boiling breaks the covalent bonds in a simple molecular liquid.
• Calling the mobile particles in graphite “ions” instead of delocalised electrons.
• Reading negative melting and boiling points in the wrong direction.
• Giving a structure type without using the evidence in the table (conduction, hardness, melting point).
• Mixing nm, mm and m in one division.
• Forgetting to square for area or cube for volume.
• Dividing by the wrong number after leaving out an anomalous result.
• Listing nanoparticle risks without linking them to size or surface area.

Next steps

• Return to the study guide for any statement where you dropped marks.
• Use the revision notes for a final recap.
• Take one of all free 10-minute diagnostics to spot gaps in other topics.
• Book a free trial class if you want a teacher to go through this with you.
• Track the rest of the course with the OCR GCSE Chemistry hub and the printable checklist.

Official syllabus

OCR specification J248, Chemistry A (Gateway Science), Cambridge OCR Level 1/Level 2 GCSE (9-1): Version 4.0, August 2026; first assessment 2018. This page draws on sub-topic C2.3 Properties of materials.