AQA GCSE Chemistry Chemistry Paper 1 (Foundation), November 2021: Question 1

✅ Correct Choices

• 01.1: Non-metallic element [1 mark]
• 01.2: Compound [1 mark]

💡 Key Knowledge

• Element: A substance consisting of only one type of atom.
• Metallic vs Non-metallic: Metals conduct electricity because they have delocalised electrons. Non-metals generally do not conduct electricity.
• Compound: Two or more different types of atoms chemically combined in fixed proportions.

🧠 Exam Technique

Highlight keywords in the prompt:

• "Only one type of atom" immediately rules out Compound and Mixture.
• "Does NOT conduct electricity" rules out Metallic element.

❌ Common Errors

Confusing compounds with mixtures. Remember: mixtures contain substances that are not chemically bonded and can be present in any proportion, whereas compounds have fixed chemical bonds.

✅ Correct Choices

• 01.3: Noble gases [1 mark]
• 01.4: The boiling points increase down the group. [1 mark]
• 01.5: Atoms [1 mark]

💡 Key Knowledge

• Group 0 Name: Noble gases (He, Ne, Ar, Kr, Xe, Rn).
• Group 0 Trend: As you go down the group, atoms get larger, meaning the intermolecular forces become stronger and require more thermal energy to break. Thus, boiling points increase.
• State: Noble gases have a full outer shell of electrons (stable octet/duplet), so they exist as single, unbonded atoms (monatomic).

🧠 Exam Technique

Process of elimination for 01.4:

• Noble gases are unreactive (inert), ruling out "very reactive".
• They don't gain electrons easily, ruling out "form negative ions".
• Relative atomic mass (Aᵣ) increases down the periodic table, not decreases.

❌ Common Errors

• Ticking Molecules for 01.5. Diatomic molecules (like O₂ or Cl₂) apply to Groups 5, 6, and 7, but never Group 0.
• Confusing Group 0 (Noble gases) with Group 7 (Halogens).

✅ Correct Answer

Empirical formula = XO₂

💡 Key Knowledge

The empirical formula gives the simplest whole-number ratio of atoms or ions of each element in a compound.

Count the visible spheres shown in the unit cell:

• Grey circles (Metal X) = 3
• Black circles (Oxygen O) = 6
• Ratio: X : O = 3 : 6 = 1 : 2

❌ Common Errors

• Writing X₃O₆ instead of simplifying to the empirical formula.
• Writing the subscript on the metal, e.g. X₂O (inverting the ratio).

📐 Step-by-Step Calculation (01.7)

Given: length of side = 2.8 nm
Formula: Surface area = (length of side)² × 6

1. Calculate area of one face:
   (2.8)² = 7.84 [1 mark]
2. Multiply by 6 faces:
   7.84 × 6 = 47.04 [1 mark]
3. Round to 2 significant figures:
   47.04 rounded to 2 s.f. = 47 [1 mark]

✅ Question 01.8 Answer

The surface area to volume ratio of the fine particle is 10 times greater [1 mark]

❌ Calculation Traps & Common Errors

• Forgetting to round: Writing 47.04 loses the final accuracy mark. Always underline "2 significant figures" in the exam paper!
• Wrong arithmetic: Doing 2.8 × 2 instead of (2.8)² is a frequent squaring error.
• Ratio misconception: Thinking smaller particles have smaller surface area to volume ratios. Smaller particles actually have a much larger proportion of their atoms on the surface.

🧠 Exam Technique

Notice the mark scheme allows an error carried forward (ECF):

"Allow an answer correct to 2 significant figures resulting from an incorrect attempt at the calculation."

Even if you make a calculation slip, showing clear working and rounding your answer properly guarantees you can still pick up the final significant figures mark!