129 SL questions available across 13 populated syllabus sections.
SL · S1.1
Introduction to the particulate nature of matter
6 questions
QUESTION 1[1 mark]
Multiple choiceFoundationNo calculatorAbout 1.5 min
Which sample consists of an element?
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Correct answer: A
Reasoning: An element contains only one type of atom and cannot be decomposed chemically. Neon is made only of neon atoms. Water is a compound, while seawater and brass are mixtures. Therefore option A is correct.
QUESTION 2[1 mark]
Multiple choiceStandardNo calculatorAbout 1.5 min
The diagrams show equal numbers of identical particles in three containers of equal volume. Which assignment of physical states is correct?
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Correct answer: B
Reasoning: X has closely packed particles in a regular arrangement, so it represents a solid. Y has closely packed particles with no fixed arrangement, so it represents a liquid. Z has widely separated particles, so it represents a gas. Option B is correct.
QUESTION 3[2 marks]
Short responseStandardCalculatorAbout 3 min
Two samples of the same ideal gas are at $300\,\mathrm{K}$ and $450\,\mathrm{K}$. Determine the ratio of their average translational kinetic energies, $\overline{E}_{k,450}/\overline{E}_{k,300}$.
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For an ideal gas, average translational kinetic energy is directly proportional to absolute temperature: $\overline{E}_k\propto T$.
A pure substance is heated at constant pressure. Use the heating curve to identify the process occurring during section B and explain why the temperature remains constant.
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Section B is the first horizontal region, so it represents melting.
Energy supplied during melting overcomes attractions between particles and increases potential energy.
The average kinetic energy does not increase, so the temperature stays constant until the phase change is complete.
Final answer: Melting; the supplied energy changes potential energy rather than average kinetic energy.
QUESTION 5[2 marks]
Short responseFoundationNo calculatorAbout 3 min
Molten sodium chloride can be decomposed by electrolysis into sodium and chlorine. Explain why sodium chloride is not an element.
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Reasoning: An element cannot be broken down into simpler substances by chemical means. Electrolysis chemically separates sodium chloride into two different elements, sodium and chlorine. Sodium chloride must therefore be a compound.
Final answer: It is a compound because chemical decomposition produces two elements.
QUESTION 6[4 marks]
Multi-partAppliedNo calculatorAbout 6 min
A sealed flask contains liquid bromine and bromine vapour at constant temperature. (a) Describe the particle arrangement and motion in each phase. (b) Explain why the amount of liquid remains constant.
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(a) In the liquid, particles are close together, disordered and move past one another. In the vapour, they are far apart and move rapidly in random directions. (b) A dynamic equilibrium is established: the rates of evaporation and condensation are equal, so there is no net change in the amount of liquid.
Final answer: (a) Liquid: close and mobile; vapour: widely separated and random. (b) Evaporation rate equals condensation rate.