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2009 HSC Notes from the Marking Centre – Senior Science



This document has been produced for the teachers and candidates of the Stage 6 course in Senior Science. It contains comments on candidate responses to the 2009 Higher School Certificate examination, indicating the quality of the responses and highlighting their relative strengths and weaknesses.

This document should be read along with the relevant syllabus, the 2009 Higher School Certificate examination, the marking guidelines and other support documents which have been developed by the Board of Studies to assist in the teaching and learning of Senior Science.

Teachers and students are advised that, in December 2008, the Board of Studies approved changes to the examination specifications and assessment requirements for a number of courses. These changes will be implemented for the 2010 HSC cohort. Information on a course-by-course basis is available on the Board’s website.

General comments

Teachers and candidates should be aware that examiners may ask questions that address the syllabus outcomes in a manner that requires candidates to respond by integrating their knowledge, understanding and skills developed through studying the course including the prescribed focus areas. It is important to understand that the Preliminary course is assumed knowledge for the HSC course.

Candidates need to be aware that the marks allocated to the question and the answer space (where this is provided on the examination paper) are a guide to the length of the required response. A longer response will not in itself lead to higher marks. Writing far beyond the indicated space may reduce the time available for answering other questions.

Candidates need to be familiar with the Board’s Glossary of Key Words which contains some terms commonly used in examination questions. However, candidates should also be aware that not all questions will start with or contain one of the key words from the glossary. Questions such as ‘how?’, ‘why?’ or ‘to what extent?’ may be asked or verbs may be used which are not included in the glossary, such as ‘design’, ‘translate’ or ‘list’.

Section I – Core

Part B

Question 16

  1. Weaker responses referred to the type of joint (ball and socket) rather than the specific body part (hip).
  2. Poorer responses identified the structure as a joint.

Question 17

  1. Better responses explained what was happening in the model, for example pulling down on the rubber sheet changes the air pressure/volume and air would enter the balloons. Some weaker responses failed to refer to the model and referred only to the respiratory system itself or just described what happens.
  2. Poorer responses gave the same reason twice rather than suggesting an alternative use of models in science. Better responses provided both the advantages and disadvantages of using models.

Question 18

  1. Better responses drew a clear diagram which represented the cells as shown photographed through the microscope, and included correct labelling of cell features (for example nucleus or cell membrane).

    Weaker responses drew simple cell diagrams with no labelling and/or had inadequate labelling.

  2. Better responses linked a role of the skin to an identified risk of surgery and how this risk could be reduced.

    Weaker responses identified only how the risk could be reduced.

Question 19

Better responses used the information in the stimulus material to justify why the optical fibre was the better choice based on the criteria of data security and transfer rates.

Weaker responses only compared one feature from the information provided or only stated features of optical fibres or copper wire.

Question 20

Superior responses distinguished between soaps and soapless detergents, often with reference to their different structures, and went on to describe a variety of beneficial and detrimental effects on the environment. Many of these responses also included a historical perspective discussing the introduction of biodegradable soapless detergents and the benefits of these to the environment.

Weaker responses confused the properties of soaps with those of soapless detergents and some only described the properties and uses of soaps and soapless detergents without mentioning any environmental effects.

Question 21

  1. Superior responses provided an appropriate linear scale on both the x and y axes, with accurately plotted points and carefully drawn lines. The lines were distinguished from each other by labels next to each line or an appropriate key. Better responses drew a neat and accurate graph and mistakes were corrected neatly. Weaker responses included bar graphs which were not appropriate for this type of data.
  2. Superior responses accounted for the increase in heart rate by relating it to the increased need for oxygen or nutrients or as a means to increase the cooling process. Weaker responses just described the increase in heart rate.

Question 22

  1. Better responses correctly changed the subject of the equation, substituted given values into it and calculated the answer with appropriate units.

    Poorer responses gave incorrect units, left units out, incorrectly manipulated the given equation or tried to use the equation as provided but made incorrect substitutions.

    Poorer responses gave unrealistic results for the signal’s time to travel to the satellite. These answers bore no relation to the theoretical knowledge about time delay.

    Better responses identified two or more advantages of using optical fibres over satellites for people talking to each other in different countries.

    Weaker responses included facts about satellites and/or optical fibres but could not relate these to their effect on conversations.

Question 23

  1. Better responses correctly identified the number of drops needed to fill the measuring cylinder to 1ml as the dependent variable.

    Poorer responses nominated independent or controlled variables or pieces of equipment or materials used as the dependent variable.

  2. Better responses identified an aspect of the investigation procedure that ensured validity.

    Poorer responses confused validity with reliability and/or accuracy or suggested future improvements that could be made to ensure validity.

  3. Better responses correctly explained how the addition of detergent reduced the surface tension in the water, leading to the drops breaking away from the dropper because they were smaller in size than water drops without detergent in them.

    Weaker responses identified the results of the investigation (increase in the number of drops) but could not link them to the correct explanation.

    Poorer responses identified changes in surface tension but did not correctly link them to the results or confused them with other aspects of detergent activity or properties.

Question 24

  1. Better responses identified clear properties of optic fibres, for example flexibility, security, total internal reflection, ability to carry large amounts of information and ability to transmit light. Weaker responses focused on properties of light.
  2. Better responses applied the ‘law of reflection’, so that when the light ray is extended in the diagram, it reflected off the upper side of the shaded cladding once, resulting in the light ray then passing out through the opening without hitting the lower shaded cladding.

    Weaker responses included more than one ray of light, a curved ray of light, or light rays that extended into the shaded sections of the fibre

Question 25

  1. The best responses identified a relevant scientific idea and linked this to the named technology.

    Weaker responses identified a relevant scientific idea or identified a relevant feature of the technology.

    Poor responses did not identify a relevant scientific idea or identify a relevant feature of the technology.

  2. The best responses identified a relevant possible future direction of scientific research and explain how the identified research could lead to an improvement of the technology.

    Weaker responses identified only a future possible direction of scientific research.

Question 26

The best responses demonstrated a thorough knowledge and understanding of all three suggested diagnostic methods and provided a supported judgement for one appropriate test.

Mid-range responses demonstrated a thorough knowledge and understanding of one or two suggested diagnostic methods and provide a specific supported judgement for one appropriate test.

Poor responses demonstrated a basic knowledge and understanding of one or two suggested diagnostic methods only.

Question 27

Better responses referred to the three distinct steps as outlined in the question, often with subheadings applied. They included a brief outline of each step, including energy changes that occurred at each of these.

Weaker responses demonstrated a limited understanding of how a fax is transmitted, with little detail, and often repeated the question in the answer with no additional information.

Section II – Options

Question 28 – Polymers

    1. Better responses gave both the meaning of the numerals and the triangle of arrows.
    2. Better responses gave a clear reason for the difficulty in recycling PVC items that contain additives.
  1. Better responses constructed an appropriate table listing the approximate percentages of the pharmaceutical products and had their sectors adding up to 100%.
  2. Better responses named a thermoset plastic. Weaker responses named a thermoplastic or answered with the generic term ‘plastic’.
    1. Better responses provided specific examples of blends and their properties.
  3. Better responses defined the term ‘decomposer’ and gave a general statement about nutrient recycling. Weaker responses merely stated that organisms in an ecosystem will decompose.
  4. Better responses outlined a relevant method of investigation that included one or more variables that could be controlled.
  5. Better responses demonstrated thorough knowledge by listing natural polymers which could be substituted for synthetic polymers of petrochemical origin. Some responses referred to the need for scientific research to produce a new type of synthetic polymer from non-petrochemical sources. The best responses also related an impact of a ban on synthetic polymers of petrochemical origin to people’s everyday lives and communicated their ideas in a coherent manner.

Question 29 – Preservatives and Additives

    1. Better responses identified that it is illegal under Australian law to add preservatives to canned foods and explained that the claim was misleading.
  1. Better responses identified sugar, salt (sodium chloride), bacteriocin, or citric acid.
    1. Better responses outlined a similarity and a difference in the preservation methods pictured. Some weaker responses incorrectly outlined similarities and differences related to the materials used in the packaging.
    2. Better responses identified a feature of each preservation method and outlined a positive impact related to this feature.
    1. Better responses outlined experiments such as scratch/spot tests, and included information to ensure it was a controlled experiment with only one variable.
  2. Better responses clearly explained the cause of food spoilage and discussed methods of food preparation that will reduce food spoilage. Weaker responses discussed only food preservation methods.

Question 30 – Pharmaceuticals

    1. Better responses included the replication of the DNA, the lengthening of the cell followed by division of the cell by the growth of a new cell wall to form ‘2 identical daughter cells’.
    1. Best responses showed clearly how Harvey’s model related to distribution of the pharmaceutical to the body tissues.
    1. Better responses named an antibiotic, identified its source and described its mode of action.
    2. Better responses referred to the need for repetition, following safety procedures and controlling variables such as temperature and period of incubation and amount of antibiotic added. These also referred to a zone of inhibition as indicating the bacteria killed by the antibiotic.
  1. Better responses demonstrated thorough knowledge of the role of prostaglandins in the inflammation response to injury or infection and in the transmission of the ‘pain signal’ across the synapse. They also related this knowledge to the effects of analgesics using a coherent and logical argument.

    Weaker responses showed some limited knowledge of the inflammation response, the synapse and the effect of analgesics.

Question 31 – Disasters

    1. Better responses explained why the events were natural and identified that the disasters were events associated with large-scale environmental or structural damage and/or loss of life.
    2. Better responses recalled the specific year and location of their named Australian disaster for example “Cyclone Tracy in Darwin in 1974”.
  1. Better responses determined the angles and calculated the correct percentages which totalled 100%.
  2. Better responses identified a named Australian disaster caused by human activity. For example the Granville train disaster.
    1. Better responses could state one of the situations and one of the provisions from the insurance policy.
    2. Better responses justified their response with reference to the insurance policy.
  3. Better responses related the closeness of the isobars to changes in air pressure over a small area. They also indicated that this produced strong winds.

    Weaker responses simply related the isobars to air pressure or to strong winds.

  4. Better responses named a weather forecasting technology and gave a description of how it leads to an improved forecast of the weather. This was then related to the issue of warning the public.

    Weaker responses simply discussed how early detection or prediction could be used to warn the public.

  5. Better responses included well-planned assessments of the advantages and disadvantages of using mobile phone messages to warn people and enable them to plan their evacuation. These responses included a judgment, and reference to an overall plan or other rescue agencies which would be part of this messaging system. Scientific descriptions of how the mobile phone network functioned were also included.

    Weaker responses only mentioned one or two advantages or disadvantages of using mobile phones, showing only basic knowledge of disaster management.

Question 32 – Space Science

    1. Better responses defined circadian rhythms and made reference to the graph and the regular changes in body temperature over a day. Weaker responses had difficulty interpreting the graph or ignored it, giving a simplistic description referring to body changes.
    2. Better responses identified two situations which would lead to disturbed circadian rhythms. Weaker responses included ways to change the body’s temperature through exercise or a bath unrelated to circadian rhythms.
  1. Stronger responses determined the angles and calculated the correct percentages which totalled 100%.
  2. Better responses identified the International Space Station as the only currently operating space station.
    1. Better responses related thermal properties of the tile to their role in the space shuttle as it re-enters the atmosphere. Weaker responses considered only the extreme heat of re-entry.
  3. Better responses identified two conditions in space that require the wearing of a space suit for protection. Weaker responses only identified properties of the space suit.
  4. Better responses showed a good understanding of the concept of space and had an informed judgement.
  5. Better responses identified at least two technologies that have developed since Galileo’s time. They explained the nature of the information and how it was gathered and why this has improved our understanding of the universe. They also identified a type of technology or named an example, such as the Hubble telescope.


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