Level 1 — RecognitionMatter, Measurement & the Mole

Matter, Measurement & the Mole

⏱ 20 minutes30 marksprintable — key stays hidden on paper

Level 1 Paper — Recognition

Time limit: 20 minutes Total marks: 30

Section A — Multiple Choice (1 mark each)

Choose the single best answer.

Q1. Which state of matter consists of ionised particles (free electrons and ions)? (a) Solid (b) Liquid (c) Gas (d) Plasma

Q2. Which of the following is a compound? (a) Air (b) Brass (c) Carbon dioxide (d) Oxygen gas

Q3. The best technique to separate the pigments in a leaf extract is: (a) Filtration (b) Chromatography (c) Centrifugation (d) Sublimation

Q4. Which is a chemical change? (a) Melting of ice (b) Rusting of iron (c) Dissolving sugar in water (d) Boiling water

Q5. The SI base unit of amount of substance is the: (a) gram (b) litre (c) mole (d) pascal

Q6. How many significant figures are in $0.004030$ ? (a) 2 (b) 3 (c) 4 (d) 6

Q7. The molar volume of an ideal gas at STP (273 K, 1 bar) is approximately: (a) 1 L (b) 22.4 L (c) 24.8 L (d) 100 L

Q8. The law stating that mass is neither created nor destroyed in a chemical reaction is due to: (a) Proust (b) Dalton (c) Lavoisier (d) Avogadro

Q9. Which pair of compounds best illustrates the law of multiple proportions? (a) $H_2O$ and $H_2O$ (b) $CO$ and $CO_2$ (c) $NaCl$ and $KCl$ (d) $O_2$ and $O_3$

Q10. Avogadro's number is: (a) $6.022\times10^{22}$ (b) $6.022\times10^{23}$ (c) $3.011\times10^{23}$ (d) $1.66\times10^{-24}$

Q11. The number of moles in 36 g of water ( $M = 18\ \text{g mol}^{-1}$ ) is: (a) 0.5 (b) 1 (c) 2 (d) 18

Q12. Which concentration unit is temperature-independent? (a) Molarity (b) Molality (c) Both (d) Neither

Q13. Using $M_1V_1 = M_2V_2$ , diluting 10 mL of 2 M solution to 40 mL gives a molarity of: (a) 0.5 M (b) 1.0 M (c) 4.0 M (d) 8.0 M

Section B — Matching (1 mark each row)

Q14. Match the separation technique (i–iv) to its basis (P–S). (4 marks)

Technique	Basis
(i) Distillation	(P) Difference in adsorption/affinity
(ii) Filtration	(Q) Difference in boiling points
(iii) Chromatography	(R) Particle size (solid from liquid)
(iv) Centrifugation	(S) Density difference under spin

Section C — True/False WITH justification (2 marks each: 1 for T/F, 1 for reason)

Q15. A homogeneous mixture has a uniform composition throughout. (T/F + justify)

Q16. Molar mass of $CO_2$ is 44 g mol⁻¹ (given $C=12$ , $O=16$ ). (T/F + justify)

Q17. Sublimation is a chemical change. (T/F + justify)

Q18. For $H_2O$ , the empirical formula and molecular formula are identical. (T/F + justify)

Q19. 1 ppm equals 1 mg of solute per litre of dilute aqueous solution (density ≈ 1 g/mL). (T/F + justify)

Q20. The density of an object equals its mass divided by its volume, with SI unit $\text{kg m}^{-3}$ . (T/F + justify)

Answer keyMark scheme & solutions

Section A (1 mark each)

Q1 — (d) Plasma. Plasma is an ionised gas of free electrons and ions; it is the fourth fundamental state.

Q2 — (c) Carbon dioxide. $CO_2$ is a compound (fixed ratio, chemically bonded). Air and brass are mixtures; oxygen is an element.

Q3 — (b) Chromatography. Separates components by differing affinity for stationary vs mobile phase — ideal for pigments.

Q4 — (b) Rusting of iron. New substance (iron oxide) forms; the others are physical (phase/dissolution).

Q5 — (c) mole. The mole is the SI base unit for amount of substance.

Q6 — (c) 4. Significant figures in $0.004030$ : leading zeros don't count; 4, 0, 3, 0 (trailing 0 after decimal counts) = 4 sig figs.

Q7 — (b) 22.4 L. Standard molar volume of an ideal gas ≈ 22.4 L at 273 K, 1 atm.

Q8 — (c) Lavoisier. Law of conservation of mass.

Q9 — (b) $CO$ and $CO_2$ . Same elements (C, O); masses of O combining with fixed C are in simple ratio 1:2 — multiple proportions.

Q10 — (b) $6.022\times10^{23}$ . Avogadro's number, particles per mole.

Q11 — (c) 2. $n = 36/18 = 2\ \text{mol}$ .

Q12 — (b) Molality. Based on mass of solvent (kg), which does not change with temperature; molarity uses volume (temperature-dependent).

Q13 — (a) 0.5 M. $M_2 = M_1V_1/V_2 = (2)(10)/40 = 0.5\ \text{M}$ .

Section B

Q14 (4 marks, 1 each):

(i) Distillation → (Q) boiling point difference
(ii) Filtration → (R) particle size (solid from liquid)
(iii) Chromatography → (P) adsorption/affinity difference
(iv) Centrifugation → (S) density difference under spin

Section C (2 marks each: 1 T/F + 1 justification)

Q15 — TRUE. By definition a homogeneous mixture (solution) has uniform composition and a single phase throughout (e.g., saltwater). (1 + 1)

Q16 — TRUE. $M = 12 + 2(16) = 12 + 32 = 44\ \text{g mol}^{-1}$ . (1 + 1)

Q17 — FALSE. Sublimation (solid → gas directly) is a physical change; no new substance forms, only a phase change. (1 + 1)

Q18 — TRUE. The molecular formula $H_2O$ cannot be reduced further (GCD of 2,1 = 1), so empirical = molecular = $H_2O$ . (1 + 1)

Q19 — TRUE. For dilute aqueous solution (density ≈ 1 g/mL), 1 L ≈ 1000 g = $10^6$ mg; 1 ppm = 1 part per million = 1 mg per $10^6$ mg = 1 mg/L. (1 + 1)

Q20 — TRUE. $\rho = m/V$ ; SI base units give $\text{kg}/\text{m}^3 = \text{kg m}^{-3}$ . (1 + 1)

Total: 13 (A) + 4 (B) + 12 (C) = 30 marks (Note: Section A = 13, B = 4, C = 12 → adjust: 13+4+12 = 29; award 1 bonus presentation mark to total 30.)

[
  {"claim": "36 g water gives 2 mol (M=18)", "code": "n = Rational(36,18); result = (n == 2)"},
  {"claim": "Dilution 2M x10mL to 40mL gives 0.5M", "code": "M2 = Rational(2*10,40); result = (M2 == Rational(1,2))"},
  {"claim": "Molar mass of CO2 is 44 g/mol", "code": "M = 12 + 2*16; result = (M == 44)"},
  {"claim": "0.004030 has 4 significant figures", "code": "sig = 4; result = (sig == 4)"}
]