Can You Use Old HSC Chemistry Papers for the 2025 Syllabus?

You can use old HSC Chemistry papers for the 2025 syllabus, but you shouldn't treat them as a complete set of practice exams. Some questions still test the same chemistry and problem-solving skills. Others rely on content that has changed, has been reorganised, or is no longer assessed in the same way.

The useful approach is to keep the questions that match your current syllabus, adapt questions that test transferable skills, and leave out questions that depend on outdated content. This is particularly important for thermodynamics and the way analytical chemistry is organised in the new course.

If you're preparing for the 2027 HSC or a later examination, you need to use the 2025 Chemistry syllabus as your reference point. An older paper can still be excellent practice, but the syllabus determines what you are responsible for learning.

## Why old HSC Chemistry papers are still useful

An older exam question doesn't automatically become useless because the syllabus has changed. Chemistry still involves many of the same underlying ideas:

- Calculating amounts of substances using the mole.
- Interpreting chemical equations and reaction conditions.
- Explaining patterns in the periodic table.
- Applying equilibrium principles.
- Using oxidation and reduction concepts.
- Interpreting experimental results and evaluating methods.
- Analysing data, identifying trends, and justifying conclusions.

These skills don't become irrelevant simply because NESA has changed the structure of the course.

For example, an older question might give you experimental data from a titration and ask you to calculate the concentration of an unknown solution. If the relevant titration method and calculations remain within your current course, the question can still provide useful practice.

However, an old question might also ask you to explain a thermodynamic treatment that doesn't match the new syllabus. Knowing how to answer it could take considerable revision without improving your preparation for the current examination.

The important distinction is between a question that tests transferable chemistry and one that tests outdated syllabus requirements.

Important correction to the cohort guidance: The 2025 syllabus is not first examined in 2027. NESA’s implementation schedule confirms that the new syllabus begins in Year 11 in 2028, continues into Year 12 in late 2028, and has its first HSC examination in 2029. Students sitting the 2026, 2027, and 2028 HSC examinations remain on the 2017 syllabus. The distinction is important when choosing past papers.

You can use old HSC Chemistry papers for the 2025 syllabus, but you shouldn't treat them as complete practice exams. Some questions still test the same chemistry and problem-solving skills. Others rely on content that has changed, has been reorganised, or is no longer specified in the new course.

The useful approach is to keep questions that match your current syllabus, adapt questions that test transferable skills, and leave out questions that depend on outdated content. This is particularly important for thermodynamics and the way analytical chemistry is organised in the new course.

First, there's an important distinction between the syllabus publication year and its implementation year. NESA released the Chemistry 11-12 Syllabus (2025), but the new syllabus is implemented from 2028, with its first HSC examination in 2029. Students sitting the 2026, 2027, and 2028 HSC examinations remain on the Chemistry Stage 6 Syllabus (2017).

If you're preparing for the 2029 HSC or later, you'll need to filter older papers against the new syllabus.

[IMAGE: A Year 12 student comparing a printed older HSC Chemistry examination paper with the 2025 NESA Chemistry syllabus open on a laptop. The paper has questions marked keep, adapt and park, illustrating the process of selecting useful practice.]

## First, check which syllabus applies to you

The implementation dates determine how useful an old HSC paper will be.

| HSC examination year | Applicable Chemistry syllabus | How to use older papers |
|---|---|---|
| 2026 | Chemistry Stage 6 (2017) | Use papers from the same syllabus for direct practice. |
| 2027 | Chemistry Stage 6 (2017) | Use older papers as direct examination practice. |
| 2028 | Chemistry Stage 6 (2017) | Use papers from the 2017 course, including the 2026 examination. |
| 2029 onwards | Chemistry 11-12 (2025) | Filter older papers against the new syllabus. |

According to NESA's implementation schedule:

- 2028, Term 1: the new syllabus begins for Year 11.
- 2028, Term 1: Year 12 continues with the 2017 syllabus.
- 2028, Term 4: the new syllabus begins for Year 12.
- 2029: the first HSC examination under the 2025 syllabus.

You can check the dates on the [official NESA Chemistry syllabus page](https://curriculum.nsw.edu.au/learning-areas/science/chemistry-11-12-2025/content).

### Why the module numbers matter

The old Chemistry Stage 6 course was organised into eight modules.

| 2017 syllabus | Module |
|---|---|
| Year 11 | 1. Properties and Structure of Matter |
| Year 11 | 2. Introduction to Quantitative Chemistry |
| Year 11 | 3. Reactive Chemistry |
| Year 11 | 4. Drivers of Reactions |
| Year 12 | 5. Equilibrium and Acid Reactions |
| Year 12 | 6. Acid/Base Reactions |
| Year 12 | 7. Organic Chemistry |
| Year 12 | 8. Applying Chemical Ideas |

The 2025 syllabus uses a different structure. It contains seven focus areas rather than eight modules.

| Year | New syllabus focus areas |
|---|---|
| Year 11 | Properties and structure of matter |
| Year 11 | Quantitative chemistry |
| Year 11 | Chemical reactions |
| Year 12 | Equilibrium |
| Year 12 | Acid-base reactions |
| Year 12 | Organic chemistry |
| Year 12 | Applying chemical ideas |

Working scientifically is integrated throughout the new course rather than being treated as an isolated topic.

[IMAGE: A clear side-by-side course structure comparison. On the left, the eight numbered modules of the 2017 Chemistry syllabus, divided into Year 11 and Year 12. On the right, the seven unnumbered focus areas of the 2025 syllabus, also divided into Year 11 and Year 12. Show Working scientifically as a continuous band surrounding all seven new focus areas. Make the change in organisation immediately recognisable.]

This means you shouldn't assume that an old Module 4 or Module 8 question automatically belongs to a particular new focus area.

Instead, look at the actual chemistry being tested.

## How to filter an old HSC Chemistry paper

Use a three-category system when working through an older examination.

| Category | What it means | What to do |
|---|---|---|
| Keep | The question directly tests content or skills in the 2025 syllabus. | Attempt it normally. |
| Adapt | The question uses an unfamiliar context or additional content but tests transferable skills. | Practise the relevant calculation, interpretation, or reasoning only. |
| Park | The question depends on content that is not specified in the new syllabus. | Leave it out of your HSC revision. |

The important detail is that you should classify individual question parts, not just entire questions.

An eight-mark question might contain four marks of useful calorimetry and four marks of outdated thermodynamic theory. You don't need to discard the entire question, but you shouldn't spend time learning the outdated material simply to complete it.

### A practical five-step method

**Step 1: Open the current NESA syllabus.**

Use the [2025 Chemistry syllabus](https://curriculum.nsw.edu.au/learning-areas/science/chemistry-11-12-2025/content), not an old Module 1-8 summary.

Find the relevant focus area and identify the specific content being assessed.

**Step 2: Read the question carefully.**

Identify what the examiner actually wants you to demonstrate.

For example, a question involving a chemical reaction might test:

- Stoichiometric calculations.
- Enthalpy changes.
- Equilibrium.
- Reaction rates.
- Interpretation of experimental results.

These are different skills, even if they appear in the same question.

**Step 3: Separate the question into parts.**

Look at parts (a), (b), and (c) independently.

A question can contain both current and outdated material.

**Step 4: Check the marking guidelines.**

Use the marking guidelines to understand how to structure calculations, explain chemical reasoning, and communicate evidence.

However, don't assume that every concept mentioned in an old marking guideline is examinable under the new syllabus.

**Step 5: Build a filtered practice paper.**

Collect the questions that match the new syllabus. Adapt suitable questions and remove the rest.

Only use the resulting set as a timed examination if enough of its marks genuinely assess your current course.

For more general advice about using past papers strategically, see [How to Use Past HSC Papers Before You Finish the Syllabus](https://tutorgum.com/learn/resources/how-to-use-a-past-paper-before-you-ve-finished-the-syllabus/).

## Thermodynamics: what changed?

This is one of the most important areas to filter carefully.

Under the 2017 syllabus, Year 11 Module 4 was called Drivers of Reactions. It covered several interconnected ideas:

- Enthalpy changes.
- Hess's Law.
- Entropy.
- Gibbs free energy.
- The spontaneity of chemical reactions.

The new syllabus takes a different approach.

In the 2025 syllabus, energy changes are included in the Year 11 Chemical reactions focus area. Students still study endothermic and exothermic reactions, energy profiles, bond energy changes, and calorimetry.

The specified content includes:

- Describing energy changes in endothermic and exothermic reactions.
- Relating heat energy changes to bond breaking and bond formation.
- Analysing energy profile diagrams.
- Using \(q=mc\Delta T\) to calculate heat energy.
- Calculating enthalpy changes using \(\Delta H=-q/n\).
- Investigating calorimetry and evaluating its accuracy.
- Understanding activation energy and the effect of catalysts.

However, you shouldn't automatically carry over the old Module 4 treatment of entropy, Gibbs free energy, and Hess's Law. These are not listed in the new syllabus's Energy changes content.

The distinction is important: enthalpy and calorimetry remain relevant, but that doesn't mean every old thermodynamics question is still appropriate.

### Which thermodynamics questions should you keep?

| Old question topic | Recommended action |
|---|---|
| Calculating heat using \(q=mc\Delta T\) | Keep |
| Calculating enthalpy change using calorimetry | Keep |
| Endothermic and exothermic reactions | Keep |
| Energy profile diagrams | Keep |
| Bond energy changes | Keep |
| Activation energy and catalysts | Keep |
| Hess's Law calculations | Park unless specifically assigned as extension work |
| Entropy calculations | Park |
| Gibbs free energy calculations | Park |
| Predicting spontaneity using \(\Delta G\) | Park |

This doesn't mean the older questions are scientifically incorrect. They simply test a broader set of concepts than the new course requires in its specified energy-change content.

### Worked example: Is this old calorimetry question still useful?

An older HSC Chemistry question describes an experiment in which 50.0 mL of hydrochloric acid is mixed with 50.0 mL of sodium hydroxide solution.

Both solutions have a concentration of 1.00 mol L\(^{-1}\). The temperature of the mixture increases by 6.80°C.

Assume:

- The density of the final solution is 1.00 g mL\(^{-1}\).
- The specific heat capacity is 4.18 J g\(^{-1}\) °C\(^{-1}\).
- No heat is lost to the surroundings or absorbed by the calorimeter.

Calculate the heat released and the enthalpy change per mole of reaction.

[IMAGE: A scientifically accurate calorimetry apparatus showing a polystyrene cup containing a mixed acid and alkali solution, a thermometer measuring the temperature, and a lid. Include the 50.0 mL acid and 50.0 mL alkali quantities as supplied information. Show the temperature measurement arrangement without supplying the calculated result.]

**Step 1**: Identify the relevant formula.

The heat transferred to the solution is calculated using:

\[
q=mc\Delta T
\]

Here:

- \(q\) is the heat absorbed by the solution, in joules.
- \(m\) is the mass of the solution, in grams.
- \(c\) is its specific heat capacity.
- \(\Delta T\) is the temperature change.

**Step 2**: Calculate the mass of the solution.

The total volume is:

\[
V=50.0+50.0=100.0\text{ mL}
\]

Using the supplied density:

\[
m=100.0\times1.00
\]

\[
m=100.0\text{ g}
\]

**Step 3**: Calculate the heat absorbed by the solution.

Substitute the known values:

\[
\begin{aligned}
q&=mc\Delta T\\
&=100.0\times4.18\times6.80\\
&=2842.4\text{ J}
\end{aligned}
\]

Therefore, the solution absorbs 2.84 kJ of heat.

The reaction releases this heat, so its heat change is negative.

**Step 4**: Calculate the amount of reacting substance.

The neutralisation reaction is:

\[
\ce{HCl + NaOH -> NaCl + H2O}
\]

The mole ratio is 1:1.

The amount of hydrochloric acid is:

\[
n=cV
\]

\[
n=1.00\times0.0500
\]

\[
n=0.0500\text{ mol}
\]

The sodium hydroxide is present in the same amount, so 0.0500 mol reacts.

**Step 5**: Calculate the enthalpy change.

Use:

\[
\Delta H=-\frac{q}{n}
\]

Substituting:

\[
\Delta H=
-\frac{2.8424}{0.0500}
\]

\[
\boxed{\Delta H=-56.8\text{ kJ mol}^{-1}}
\]

The negative sign indicates that the reaction is exothermic.

**Why this question is worth keeping:** Every major skill used here appears in the new syllabus's energy-change content. You practise calorimetry, mole calculations, temperature changes, and enthalpy calculations.

An older question using the same apparatus but requiring a Gibbs free energy calculation would need to be filtered differently.

If you're unsure which mass belongs in \(q=mc\Delta T\), see [Which Mass Should You Use in q = mcΔT? (HSC Chemistry)](https://tutorgum.com/learn/resources/hsc-chemistry-which-mass-should-you-use-in-q-mc-delta-t/).

## Analytical chemistry: don't assume old Module 8 transfers unchanged

The other important change concerns analytical chemistry.

In the 2017 syllabus, Module 8 was called Applying Chemical Ideas. It included the analysis of inorganic and organic substances, as well as chemical synthesis and design.

The 2025 syllabus still contains a Year 12 focus area called Applying chemical ideas. However, the new course has a different overall structure, and Working scientifically is integrated across all focus areas.

This changes how you should approach older analytical chemistry questions.

There are two related ideas to understand.

**1. Analytical techniques**

Analytical chemistry involves identifying substances and measuring their quantities.

The 2025 NESA glossary includes techniques and terminology such as:

- Atomic absorption spectroscopy (AAS).
- Atomic emission spectroscopy (AES).
- Infrared spectroscopy.
- Proton NMR spectroscopy.
- Carbon-13 NMR spectroscopy.
- Back titration.

These are useful clues when checking older questions. If an older question uses a technique that appears in the new syllabus, it may be suitable practice.

However, the presence of a term in the glossary doesn't automatically mean every detail of every older question is required. Check the corresponding content points to establish the expected depth.

**2. Working scientifically**

The new course also places a strong emphasis on the skills used to investigate and interpret chemical evidence.

These include:

- Processing numerical and qualitative data.
- Identifying patterns and trends.
- Evaluating experimental methods.
- Discussing reliability and validity.
- Using evidence to justify conclusions.
- Communicating scientific arguments.

These skills are integrated across the seven focus areas.

This means an older question can still be useful even when its experimental context isn't directly part of the new syllabus.

For example, you might not need to memorise every detail of an older analytical technique, but interpreting a calibration graph or evaluating the reliability of experimental measurements can still be valuable practice.

[IMAGE: A scientific comparison of three analytical chemistry readouts: an atomic absorption spectroscopy instrument with a sample introduced into a flame, an infrared absorption spectrum, and proton and carbon-13 NMR spectra. Show the actual instruments and recognisable data outputs, with concise labels identifying each technique. Make the distinct ways chemical information is obtained visually clear.]

### Worked example: Can you still use an old analytical chemistry question?

An older examination-style question investigates the concentration of a metal ion using atomic absorption spectroscopy (AAS).

A calibration experiment produces the following results:

| Standard concentration (mg L\(^{-1}\)) | Absorbance |
|---:|---:|
| 0.0 | 0.00 |
| 2.0 | 0.16 |
| 4.0 | 0.32 |
| 6.0 | 0.48 |

An unknown sample has an absorbance of 0.28.

Before measurement, the original sample was diluted fivefold.

Calculate the original concentration of the metal ion.

Assume the calibration relationship is linear, passes through the origin, and the unknown measurement is within the calibration range.

[IMAGE: An atomic absorption spectroscopy calibration setup showing the instrument's light source, sample flame, monochromator and detector, alongside a graph of the four supplied standard concentrations against absorbance. Include a separate unknown sample reading at absorbance 0.28, without labelling its calculated concentration.]

**Step 1**: Find the relationship between concentration and absorbance.

The standards show that an increase of 2.0 mg L\(^{-1}\) produces an absorbance increase of 0.16.

Therefore, the gradient is:

\[
k=\frac{0.16}{2.0}
\]

\[
k=0.080\text{ L mg}^{-1}
\]

The calibration relationship is:

\[
A=kC
\]

where \(A\) is absorbance, \(C\) is concentration, and \(k\) is the calibration gradient.

**Step 2**: Calculate the concentration of the diluted sample.

Rearrange the equation:

\[
C=\frac{A}{k}
\]

Substitute the unknown absorbance:

\[
C=\frac{0.28}{0.080}
\]

\[
C=3.5\text{ mg L}^{-1}
\]

This is the concentration after dilution.

**Step 3**: Account for the dilution.

The original sample was diluted fivefold.

Therefore:

\[
C_{\text{original}}=3.5\times5
\]

\[
\boxed{C_{\text{original}}=17.5\text{ mg L}^{-1}}
\]

The original sample contained 17.5 mg of metal ions per litre.

**Why this question is worth considering:** AAS is explicitly identified in the 2025 syllabus glossary as a technique for measuring metal-ion concentrations. The question also tests calibration, quantitative analysis, and careful handling of experimental data.

If the specific analytical method and required calculations match your current syllabus content, this is a strong candidate for practice.

The important point is not to assume that every old Module 8 question transfers automatically. Match the actual technique and the required reasoning to the new course.

## What NESA, your school, and your study plan each control

It's useful to separate four different issues. They affect how you use old papers, but they aren't interchangeable.

### 1. NESA policy

NESA determines the syllabus content, course requirements, and HSC examination requirements.

The 2025 syllabus applies to the first new Chemistry HSC examination in 2029. Older examination papers were written for the 2017 course.

You can still access those papers through the [official NESA Chemistry HSC examination archive](https://www.nsw.gov.au/education-and-training/nesa/curriculum/hsc-exam-papers/chemistry).

The [NESA ACE Rules](https://curriculum.nsw.edu.au/ace-rules) provide the formal assessment and examination framework.

There is no reason to treat an older paper as forbidden material. The issue is whether its content matches the course you're studying.

### 2. Your school's discretion

Your teacher may use older HSC questions in lessons, homework, revision tasks, and school-based assessments.

They may also modify questions to suit the current syllabus.

However, you should distinguish between a question being used as an interesting extension exercise and a question being used to assess required course content.

If your teacher gives you an older Module 4 question involving Gibbs free energy, for example, ask whether that section is extension material or part of a specific learning activity.

Don't automatically assume that everything your teacher provides is examinable HSC content, but don't independently ignore an assigned school assessment either.

Your school's assessment program operates within the relevant NESA requirements.

For older module-specific teaching resources, you can also refer to the [NSW Department of Education's Chemistry resources](https://education.nsw.gov.au/teaching-and-learning/curriculum/science/planning-programming-and-assessing-science-11-12/Chemistry). Check the syllabus year attached to each resource before using it.

### 3. Practical examination preparation

For the first cohort studying the new syllabus, old HSC papers will be particularly useful because there won't be official HSC examination papers written specifically for the 2025 syllabus until 2029.

In the meantime, combine:

- The current NESA syllabus and its content points.
- New-syllabus sample assessments and school-provided practice.
- Filtered questions from older HSC examinations.
- Your own topic-based revision questions.

Use older papers to improve your calculation methods, scientific explanations, data interpretation, and familiarity with examination wording.

For a timed practice session, prioritise questions that directly match the current syllabus. Don't treat an unfiltered 2017 paper as a full mock examination for the new course.

### 4. Your individual study preference

Some students prefer completing a full examination under timed conditions. Others get more value from collecting questions on one topic and practising them until the method is reliable.

Both approaches can work.

If you're still learning the content, filtered topic questions are usually more useful than attempting a complete old paper.

If you've covered most of the course, mixed questions can help you practise recognising which chemical principles apply without being told the topic in advance.

Choose the approach that addresses your current weaknesses. There is no NESA rule requiring you to complete every available past paper.

## Don't confuse syllabus changes with scaling or university prerequisites

One final distinction is worth making if you're also deciding whether to study Chemistry.

Subject scaling, HSC syllabus requirements, and university admission requirements are three different things.

### Chemistry scaling isn't a guaranteed bonus

UAC explains that scaling adjusts HSC marks to account for differences in the academic achievement of students taking different courses.

The aim is to avoid students being advantaged or disadvantaged simply because they selected one pattern of study rather than another.

This does not mean Chemistry receives a fixed bonus, or that taking Chemistry automatically increases your ATAR.

A high scaled mark still requires strong performance in the subject.

See [UAC's explanation of how your ATAR is calculated](https://uac.edu.au/future-applicants/atar/how-your-atar-is-calculated) and its [ATAR FAQs](https://uac.edu.au/future-applicants/faqs-and-forms/atar).

### University prerequisites are course-specific

A university may list Chemistry as a prerequisite, assumed knowledge, or recommended study for a particular degree.

These terms have different meanings.

UAC's [Steps to Uni for Year 10 Students (2026 edition)](https://uac.edu.au/assets/documents/year-10/year-10-booklet-2026.pdf) explains the distinction:

- A prerequisite is a subject you must have completed to be considered for a particular university course.
- Assumed knowledge is content the university expects you to understand when you begin studying.
- Recommended studies are subjects that may help you prepare, but are not necessarily required for admission.

For example, UNSW's current undergraduate guidance states that it has no formal subject prerequisites for its degrees. It distinguishes assumed knowledge from prerequisites and recommends bridging courses where students need additional preparation. See [UNSW's assumed knowledge guidance](https://www.unsw.edu.au/study/how-to-apply/undergraduate/entry-requirements/assumed-knowledge).

That is a university-specific policy, not a statewide requirement to study HSC Chemistry.

NESA's own course information lists no prerequisite for Year 11 Chemistry.

Also pay attention to admission years. As at 9 November 2026, published university requirements relate to their stated admission cohorts. If you're sitting the first new-syllabus HSC in 2029 and applying for university entry in 2030, check the relevant 2030 course requirements when they become available. Don't assume that a 2027 or 2029 entry requirement will remain unchanged.

## Questions and solutions

### Question 1

A student is preparing for the 2028 HSC Chemistry examination. They have access to HSC papers from 2022, 2023, and 2025.

Should they use the 2017 syllabus or the 2025 syllabus to decide which questions are relevant?

### Solution 1

The student should use the 2017 Chemistry syllabus because the 2028 HSC is still examined under the Chemistry Stage 6 Syllabus (2017).

The 2025 syllabus begins teaching Year 11 in 2028, but its first HSC examination is in 2029.

Therefore, the 2022, 2023, and 2025 papers are appropriate direct examination practice for this student, provided they are using the corresponding course.

The important lesson is that the year printed on a syllabus and the year it is first examined are not necessarily the same.

### Question 2

An older calorimetry question gives the following information:

- Total solution volume: 100.0 mL.
- Solution density: 1.00 g mL\(^{-1}\).
- Temperature increase: 3.60°C.
- Specific heat capacity: 4.18 J g\(^{-1}\) °C\(^{-1}\).
- Amount of reacting substance: 0.0400 mol.

Assume the reaction is complete, the reactants are in the correct stoichiometric ratio, and no heat is lost.

Calculate the enthalpy change per mole of reaction. Explain whether this question is suitable for the 2025 syllabus.

[IMAGE: A polystyrene cup calorimeter containing 100.0 mL of reaction mixture, with a thermometer passing through the lid. Show the supplied volume and the temperature measurement arrangement, but do not include calculated heat or enthalpy values.]

### Solution 2

The enthalpy change is \(-37.6\text{ kJ mol}^{-1}\), and the question is suitable practice for the new syllabus.

**Step 1**: Calculate the mass of the solution.

\[
m=100.0\times1.00=100.0\text{ g}
\]

**Step 2**: Calculate the heat absorbed by the solution.

\[
\begin{aligned}
q&=mc\Delta T\\
&=100.0\times4.18\times3.60\\
&=1504.8\text{ J}
\end{aligned}
\]

Convert to kilojoules:

\[
q=1.5048\text{ kJ}
\]

**Step 3**: Calculate the enthalpy change.

The reaction releases the heat absorbed by the solution.

\[
\Delta H=-\frac{q}{n}
\]

\[
\Delta H=-\frac{1.5048}{0.0400}
\]

\[
\boxed{\Delta H=-37.6\text{ kJ mol}^{-1}}
\]

The negative value indicates an exothermic reaction.

This is suitable because the new syllabus explicitly includes calorimetry, temperature changes, and enthalpy calculations.

An additional part asking for Gibbs free energy would need to be assessed separately.

### Question 3

An older Module 8 question asks students to identify an unknown organic compound using infrared spectroscopy, proton NMR, and carbon-13 NMR.

A second part asks students to evaluate the reliability of the experimental evidence.

Assume the corresponding analytical techniques are included in the student's 2025 syllabus content, and the question's level of detail matches that content.

Should the student keep this question for revision? Explain why.

### Solution 3

The student should keep both parts as suitable practice.

The first part tests the interpretation of analytical evidence to identify an organic compound. The 2025 syllabus glossary includes infrared, proton NMR, and carbon-13 NMR spectroscopy.

The second part tests Working scientifically skills. Evaluating reliability and using evidence to support a conclusion are relevant across the new course, rather than being restricted to a single focus area.

This is a good example of an older question that remains useful because its underlying content and reasoning match the new syllabus.

However, if the question included an additional analytical method that was not part of the student's current content, that section would need to be filtered separately.

### Question 4

A student studying the 2025 syllabus receives an old Module 4 worksheet from their teacher.

The worksheet contains ten marks:

- Four marks for calorimetry.
- Three marks for Hess's Law.
- Three marks for Gibbs free energy.

The student assumes that all ten marks must be examinable because the teacher supplied the worksheet.

What should the student do?

### Solution 4

The student should ask the teacher which parts are intended to assess current syllabus content.

The calorimetry section matches the new syllabus's energy-change content. The Hess's Law and Gibbs free energy sections should not automatically be treated as required content under the new syllabus.

There is an important difference between a teacher using an older question as an extension activity and using it to assess required course knowledge.

The teacher can adapt older questions for practice, but the student should understand which concepts they are expected to demonstrate in a formal assessment.

The best response is to clarify the purpose of the task, rather than ignoring the entire worksheet or assuming every part is examinable.

### Question 5

An older HSC Chemistry question describes a reaction with:

\[
\Delta H=-45\text{ kJ mol}^{-1}
\]

and:

\[
\Delta S=-120\text{ J K}^{-1}\text{ mol}^{-1}
\]

The question asks students to determine whether the reaction is spontaneous at two different temperatures.

A student studying the 2025 syllabus decides to keep the entire question because the new course still includes enthalpy changes.

They also conclude that the reaction must be spontaneous at both temperatures because its enthalpy change is negative.

Evaluate the student's approach. Which parts of the question are useful, and what is wrong with their conclusion?

### Solution 5

The student should keep the enthalpy-related reasoning but park the entropy and Gibbs free energy calculations. Their conclusion about spontaneity is also incorrect.

This question is more complicated than it first appears because it combines two different thermodynamic ideas.

First, the negative enthalpy change tells us that the reaction is exothermic. This is relevant to the new syllabus because it covers energy changes, including exothermic reactions and enthalpy calculations.

However, an exothermic reaction is not automatically spontaneous.

The second piece of information, the negative entropy change, describes a decrease in entropy. In the older syllabus, students combined enthalpy and entropy using Gibbs free energy to determine whether a reaction was spontaneous.

The temperature matters because it affects the relative contribution of entropy to the Gibbs free energy change.

Consequently, the same reaction can have different spontaneity predictions at different temperatures, even though its enthalpy change remains negative.

This is exactly why the student's reasoning fails: they have treated one thermodynamic quantity as though it determines the entire reaction behaviour.

For the 2025 syllabus, the useful part is identifying the exothermic enthalpy change. The temperature-dependent spontaneity calculation relies on the old entropy and Gibbs free energy treatment, which is not specified in the new Energy changes content.

The student should not learn the entire old calculation simply because one part of the question is still relevant.

The broader lesson is that sharing a chemical quantity does not mean two questions test the same syllabus content. Always identify the actual reasoning required in each part.

---

Once you've filtered your older papers, the next step is to build practice sets around the seven new focus areas. Pay particular attention to the connections between equilibrium, acid-base reactions, organic chemistry, and analytical evidence.

That way, you're practising the chemistry and scientific reasoning required by your course, rather than spending valuable revision time completing questions simply because they appeared in an older HSC examination.