HSC Investigating Science 2024

[3 marks]. The technology is the microwave oven. Percy Spencer was working with magnetrons that generate microwaves for radar systems. He noticed that a chocolate bar in his pocket melted while he stood near an operating magnetron. Recognising that the microwaves were heating the food, he deliberately directed them at other foods (such as popcorn), and this serendipitous observation was developed into the domestic microwave oven.

Marker's note. Use a precise term for the technology (the microwave oven, not just "a microwave") and outline the radar/magnetron circumstances and the melted-chocolate observation that led to it.

[3 marks]. Vaccinating children early gives them immunity before they are exposed, so they contract fewer infectious diseases across their lives. Because vaccinated children do not catch or transmit the pathogen, the spread of disease through the community is reduced, and a high vaccination rate produces herd immunity that also protects unvaccinated members (for example, newborns and the immunocompromised). Over time this lowers the global burden of preventable disease, reduces deaths and has allowed some diseases to be controlled or eradicated, improving world health overall.

Marker's note. Use correct scientific language (immunity, herd immunity, transmission) and explicitly link the effect of the programs to an improvement in world health, not just to individual children.

[4 marks]. Both graphs are presented to flatter Brand A. In Graph 1, the vertical axis begins at 48% rather than 0, which exaggerates the visual difference between Brand A and the other brands, making Brand A's share look far larger than it is; the brand percentages also add to more than 100%, which is impossible and signals the data are unreliable. In Graph 2, the genuine (actual) malfunction-call data stop at 2021 and the years after are shown as projected values that trend downward, implying the engine problem is being resolved when no real data support this; suppressing the recent actual figures hides whether malfunctions are still high. By misrepresenting the share and projecting an unsupported improvement, the company presents itself in a more positive light than the evidence justifies, improving its public image.

Marker's note. Refer to specific features of both graphs (the truncated axis and over-100% total in Graph 1, the actual-versus-projected split in Graph 2) and link each to misrepresentation and to the company's public image.

[3 marks]. Aboriginal Peoples have long used the Kakadu plum as a food and to treat skin ailments, using its fruit and bark. This knowledge is valued by the scientific community because it points researchers directly to plants with proven, real-world benefits: scientific testing has since shown the Kakadu plum has an exceptionally high vitamin C content and strong antioxidant activity, which has led to its use in health products and skin creams. Drawing on tens of thousands of years of observation, this knowledge saves time, guides where to look for active compounds, and lets researchers investigate and verify the plant's efficacy.

Marker's note. Name a specific native plant and a specific use, and distinguish the scientific community's perspective (testable efficacy, guiding research) from Aboriginal and Torres Strait Islander Peoples' knowledge rather than blurring the two.

[4 marks]. Diathermy (electrosurgical) forceps use a high-frequency electric current to cut tissue and to coagulate (seal) blood vessels at the same time. During surgery the surgeon uses the device both to incise and to stop bleeding, rather than swapping between a separate scalpel and clamps. This reduces blood loss, shortens operating time and lowers the risk of infection, all of which improve patient safety and recovery. A minor drawback is the risk of burns or smoke if used incorrectly, and it needs trained staff and electrical equipment. On balance, the device has a strongly positive impact on human wellbeing because the benefits to surgical safety and recovery clearly outweigh the manageable risks.

Marker's note. Identify a genuine surgical device (not a procedure), describe how it is used in surgery, and provide a judgement that explicitly weighs its impact on human wellbeing.

(a) [1 mark]. Numerology is the belief that numbers (such as those derived from a person's name or birth date) have hidden significance and can influence or predict events in people's lives.

(b) [3 marks]. Numerology is a pseudo-science because its claims cannot be tested or verified using the scientific method: there is no reproducible evidence, no testable hypothesis and no mechanism linking numbers to outcomes, and it is not supported by peer-reviewed research. It also borrows the language and appearance of science (calculations, "readings") to seem credible and persuade people, while its predictions are vague enough that they cannot be falsified. Because it adopts the trappings of science without the evidence base or self-correcting process, it is classified as a pseudo-science.

Marker's note. In (b) link the specific features of pseudo-science to numerology: not validated by the scientific method, no supporting scientific papers, and use of scientific-sounding language to mislead.

(a) [2 marks]

The investigation could be conducted ethically only if recognised animal-ethics guidelines are followed: the lizards must not be harmed or stressed, must be kept in suitable conditions for the short test period, and must be returned to their natural habitat afterwards. Provided the animals are treated humanely and their welfare is protected, removing them briefly to count flies caught is ethically acceptable.

(b) [2 marks]

There is no significant relationship between tongue length and the number of flies caught. The counts are all very close (from 44 for the extra-short lizard to 47 for the extra-long lizard, a spread of only 3 flies out of 50), so tongue length does not meaningfully affect a lizard's ability to catch flies in this investigation.

(c) [4 marks]

• Repeat the trials for each lizard several times (and use more lizards at each tongue length). One reading per lizard cannot show consistency; repeating improves the reliability of the results.
• Measure tongue length quantitatively (for example in millimetres) instead of vague categories such as "short" and "long". Numerical data improve the accuracy and let a real relationship be detected.
• Control the time since each lizard last fed (and other variables such as fly species and temperature). A hungrier lizard may catch more flies regardless of tongue length, so standardising this improves the validity of the conclusion.

Marker's note. Treat "ethical" in (a) as distinct from valid or reliable. In (b) state the conclusion and quote the data. In (c) give three clear modifications and link each one specifically to reliability, validity or accuracy.

(a) [7 marks].

1. Connect a gas-pressure sensor to a data logger, and seal a fixed amount of air inside a syringe attached to the sensor.
2. Keep the syringe (and gas) at constant room temperature throughout, and use the same fixed mass of gas (do not let any leak) so volume is the only independent variable changed.
3. Record the starting volume read from the syringe scale and the pressure shown on the data logger.
4. Push the plunger in to a smaller volume, wait for the gas to return to room temperature, then record the new volume and pressure.
5. Repeat step 4 for a range of decreasing volumes, collecting at least six volume-pressure pairs across the range.
6. Repeat the whole set of readings several times and average the pressure at each volume to improve reliability.
7. Process the data: tabulate pressure against volume, and also calculate the product (pressure x volume) and 1/volume to test the relationship.
8. Plot pressure against volume (and pressure against 1/volume) to determine and confirm the relationship.

Validity is managed by controlling temperature and gas amount so that only volume affects pressure; reliability is managed by repeating the readings and averaging.

(b) [2 marks]. Keeping the temperature constant throughout is the key step for validity. The pressure of a gas depends on both temperature and volume, so if the temperature were allowed to change, any pressure change could not be attributed to the volume change alone. By holding temperature constant, volume is the only variable affecting pressure, so the investigation actually tests the pressure-volume relationship and the results are valid.

(c) [2 marks]. Pressure on the vertical axis and volume on the horizontal axis, showing an inverse relationship: as volume increases, pressure decreases along a smooth curve (a rectangular hyperbola, since pressure x volume is constant at fixed temperature).

Marker's note. Write a logical sequence of repeatable steps (not a vague outline), make clear the data are quantitative, and address reliability (repeat and average) and validity (control temperature) as distinct ideas. The graph must show a clear inverse relationship with labelled axes.

[4 marks]. Jenner observed that milkmaids who had caught the mild disease cowpox seemed protected from deadly smallpox. He tested this by inoculating a boy with material from a cowpox sore, then later exposing him to smallpox on several occasions; the boy did not develop the disease, demonstrating that cowpox inoculation produced protection. This was the key event because it was the first deliberate, evidence-based vaccination, and it laid the foundation for the science of immunisation. Building on Jenner's work, a worldwide smallpox vaccination program was eventually able to eradicate the disease completely, the only human disease so far eliminated, showing the global importance of these events.

Marker's note. Describe Jenner's cowpox inoculation and the test on the boy, explain why it was significant (the first vaccine, the basis of later programs), and link it to the worldwide eradication of smallpox. Note that a vaccine prevents rather than cures disease.

[4 marks]. For (Student A): space research has produced widely used spin-off technologies that solve problems on Earth, such as improved water-purification methods, satellite-based weather prediction and GPS navigation, and it advances scientific understanding. These benefits support continued funding. Against (Student B): the money could instead be directed at pressing social problems like poverty and world hunger, which have immediate human impact, and some argue these should take priority. Weighing both: space-exploration budgets are in fact far smaller than spending on social-welfare programs, so cutting space research would free comparatively little money while sacrificing significant scientific and technological gains that themselves benefit society. On balance, continuing funding is justified, provided it is kept in proportion alongside genuine investment in social needs.

Marker's note. Give supported points both for and against using each student's view, draw on your own examples (spin-off technologies, relative budget size), and discuss the issue rather than just stating a personal opinion.

(a) [1 mark]. Increasing the amount of water provided to a seedling increases its gain in mass over the growth period.

(b) [3 marks].

Group 1 gained about 1.0 to 1.5 g each; Group 2 (more water) gained 2.5 g each.

(c) [2 marks]. The students found that the seedlings gained mass and that the group given more water gained more, suggesting plant mass increase is related to the water supplied. Van Helmont, by contrast, grew a willow in a known mass of soil for years and found the plant gained a large mass while the soil mass barely changed, leading him to conclude the gain came from water rather than the soil. The students' result is consistent with water mattering, but, unlike van Helmont, they did not measure the soil at all.

(d) [3 marks]. The investigation is not a valid test of van Helmont's conclusion. Van Helmont's conclusion concerned the source of the added mass (water versus soil), which he tested by weighing the soil before and after. The students never weighed the soil, so they cannot show where the mass came from. They also changed the water amount between the two groups and used small seedlings rather than a single tree, introducing a different variable instead of replicating his method. Because their design does not test the same idea or control the relevant variable, it does not validly test van Helmont's conclusion, even though it does show water affects growth.

Marker's note. Write the hypothesis as one clear statement, lay the table out with headings, units and the calculated mass change, and in (d) judge validity against what van Helmont actually tested (weighing the soil) rather than against general experimental features.

(a) [3 marks]. Plot speed (m s^-1) on the horizontal axis and distance (m) on the vertical axis, using a consistent scale on each axis. Mark each point with a small cross. The point (0.77, 0.15) sits well below the trend and is an outlier, so the line of best fit should be drawn through the remaining points (which rise roughly linearly through the origin) and ignore that outlier.

(b) [3 marks]. The gradient is rise over run, distance divided by speed:

Because metres divided by metres-per-second leaves seconds, the gradient represents the time the ball was in the air (the fall time) as it travelled from the bench to the floor, which is the same for every trial since they fall the same height.

Marker's note. Put the dependent variable (distance) on the y-axis, draw a line of best fit that omits the (0.77, 0.15) outlier, and carry the units through the gradient calculation so it is clear the slope (in seconds) represents the fall time.

(a) [2 marks]. A key methodological issue is the small sample and short duration: only 10 people per group over two weeks is too few and too brief to detect a real difference in glycaemic control, lowering reliability. The study also did not control other variables that affect blood sugar, such as participants' pre-existing health conditions, overall diet and exercise, so any difference (or lack of difference) cannot confidently be attributed to the type of bread.

(b) [3 marks]. A conflict of interest exists because the authors are paid by a company that sells gut-bacteria products, so they may benefit financially from a particular conclusion. This could bias the study: it may have influenced the authors to emphasise the suggestion that glycaemic control depends "solely on gut bacteria" rather than the bread, a conclusion that conveniently supports their company's products and is not actually established by the data. Even if the work was done honestly, the conflict undermines confidence in the objectivity of the interpretation, which is why it must be declared so readers can judge the findings critically.

Marker's note. In (a) describe a genuine methodology issue and a feature of it (small sample, short trial, uncontrolled variables). In (b) show understanding of conflict of interest and link it to a specific outcome of this study (the gut-bacteria suggestion favouring the company).

[5 marks]. Governments strongly shape university research budgets because much research depends on competitive government grants rather than guaranteed funding. Since government money is limited, funding bodies favour research that aligns with national priorities, so the government effectively decides which fields and projects are supported and which are not. Grants are usually awarded for a fixed, often short, term, so researchers must show results and reapply to continue; if a project no longer matches government priorities it can lose funding and be cut short, affecting the direction and duration of research, not just its size.

For example, the Australian Research Council (ARC) awards competitive government grants to universities. A grant approved for sustainable-polymer research at an Australian university succeeded because it aligned with government priorities around sustainability; other projects that do not fit current priorities can miss out. This shows governments influence the type, direction, scale and timeframe of university research through how they allocate and renew funding.

Marker's note. Link government funding decisions to a specific, relevant example (such as an ARC or NHMRC grant tied to national priorities), and explain the impact on the project's budget, direction and timeframe rather than discussing unrelated cases.

[7 marks]

A rigorous trial of copper bracelets needs a control group, a placebo and a double-blind design.

Control group

A large group of arthritis patients is divided into a test group that wears real copper bracelets and a control group that is treated identically except they do not receive the active treatment. The two groups should have a similar mix of patients (age, severity of arthritis) so that the only difference is the copper. The control group provides a baseline of how the patients' pain changes anyway (for example due to natural fluctuation), so any real effect of copper can be measured against it.

Placebo

The control group is given placebo bracelets that look and feel identical to the copper ones but are not made of copper. This is essential because patients' pain reports can improve simply from expecting a treatment to work (the placebo effect). By comparing real copper against an indistinguishable placebo, the trial separates a genuine effect of copper from the psychological effect of wearing "a treatment".

Double-blind trial

Neither the patients nor the researchers assessing the pain know who has the real copper and who has the placebo; the bracelets are coded and randomly allocated, and the code is broken only after data collection. This prevents bias, since patients cannot be swayed by knowing their group and researchers cannot (consciously or not) influence or interpret the pain reports to favour an expected result.

Used together, the control group, placebo and double-blind design ensure that any difference in pain relief can be attributed specifically to the copper itself, giving a valid and reliable test of the claim.

Marker's note. Define placebo, double-blind trial and control group precisely, propose how each is used in this specific copper-bracelet trial, and justify why each is needed (baseline, removing the placebo effect, preventing bias). Use scientific terms throughout.