AQA GCSE Chemistry Chemistry Paper 1 (Foundation), June 2024: Question 1

✅ Correct Answers

01.1: Tick box D [1 mark]

01.2: Tick box C [1 mark]

💡 Key Knowledge

• Element: Contains only one type of atom (e.g., single black circles or paired white circles).
• Compound: Two or more different types of atoms chemically bonded together in a fixed ratio.
• Pure substance: Contains only one type of particle (all molecules/atoms are identical).
• Mixture: Two or more different substances not chemically combined.

🧠 Diagram Breakdown

• A: Mixture of two compounds (linear 3-atom molecules + bent 3-atom molecules).
• B: Mixture of two elements (single black atoms + diatomic white molecules).
• C: Mixture of an element (diatomic white molecules) and a compound (triatomic grey/white molecules).
• D: Pure compound (every single molecule is identical: 1 black atom bonded to 2 white atoms).

❌ Common Errors

• Confusing diatomic elements (like O₂ or Cl₂) with compounds. Two identical circles bonded together represent an element, not a compound!
• Mixing up Box A and Box D: Box A has two distinct kinds of molecules, making it a mixture.

✅ Correct Answer

Tick: Sections A, B and C [1 mark]

💡 Key Knowledge

The "stepped line" divides metals from non-metals:

• Section A: Reactive metals (Groups 1 and 2: alkali and alkaline earth metals).
• Section B: Transition metals.
• Section C: Metals under the stepped staircase (e.g., aluminium, tin, lead).
• Section D: Non-metals (including halogens and noble gases) located to the right of the staircase.

❌ Common Errors

Students often choose "Section B only" because they think only transition elements are metals, forgetting that Groups 1, 2, and the lower parts of Groups 3–6 are also metals.

✅ Correct Answers

• Can be bent and shaped [1 mark]
• Good conductor of electricity [1 mark]

💡 Key Knowledge

Transition metals have typical metallic properties:

• Malleable (can be bent and hammered into shape) because layers of metal ions slide over each other.
• Good electrical and thermal conductors due to delocalised electrons free to move throughout the structure.
• High melting points and high densities (unlike Group 1 alkali metals, which have low densities and low melting points).

🧠 Exam Technique

The question says "Tick two boxes". Always verify you have marked exactly two boxes. If you tick more, you risk losing marks to cancellation.

✅ Correct Answer & Mark Scheme

• Mark 1: Potassium ion [K]⁺ drawn with an empty outer shell (or with 8 outer electrons).
• Mark 2: Chloride ion [Cl]⁻ drawn with 8 outer electrons (7 crosses and 1 dot, or 8 dots/crosses showing the transferred electron).

📐 Step-by-Step Drawing Guide

1. Potassium atom: Starts with 1 dot on its outer shell (Group 1).
2. Chlorine atom: Starts with 7 crosses on its outer shell (Group 7).
3. Transfer: The single electron from potassium transfers to chlorine.
4. Potassium ion [K]⁺: Leave the outer shell ring completely empty (demonstrating loss of the single outer electron).
5. Chloride ion [Cl]⁻: Draw 8 electrons on the outer shell ring: 7 crosses (×) and 1 dot (•) to clearly show where the gained electron came from.

❌ Common Errors

• Leaving the potassium electron on the potassium ring instead of showing it transferred.
• Drawing covalent overlap (overlapping rings with shared pairs) instead of separate bracketed ions.
• Drawing fewer or more than 8 electrons on the chloride ion.

🧠 Examiner Insight

Examiners accept either an empty shell or a full shell of 8 electrons for the metal ion [K]⁺, but leaving it empty is the safest and clearest way to show the loss of the single outer electron.

✅ Correct Answers

01.6 (Collect water from NaCl solution): Tick box B [1 mark]

01.7 (Shows filtration): Tick box A [1 mark]

💡 Function of Each Apparatus in Figure 3

• A (Filtration): Separates an insoluble solid from a liquid using filter paper and funnel.
• B (Simple Distillation): Separates and collects a dissolved liquid solvent (water) from a soluble solid solution (NaCl).
• C (Paper Chromatography): Separates mixtures of soluble substances (e.g., inks/dyes).
• D (Crystallisation / Evaporation): Obtains the solid solute (salt crystals) by boiling off the liquid into the air.

❌ Common Error in 01.6

Many students incorrectly pick D (Evaporating basin). While D is used for salt solution, heating it lets water evaporate into the air to leave dry salt. To collect the water, you must use distillation (B) with a condenser.

🧠 Exam Tip: Look at the Target Product

• Want the solid solute? → Use Crystallisation / Evaporation (D).
• Want the liquid solvent? → Use Simple Distillation (B).