MYP Chemistry · Assessment guide
Criteria-based learning
Know what each criterion rewards. Plan, process and argue the way the marks are awarded.
Every MYP science task is judged against four criteria. This guide explains what each criterion rewards, shows how the on-screen examination turns the criteria into marks, and gives worked examples taken from past examination tasks with their official marking guidance. Use it alongside the seven topic chapters: each chapter ends its sections with a criterion lens showing how that chemistry is assessed.
01 / The big picture
Four criteria, one subjectCriteria A–D
In most school courses a test asks one question: do you know the content? MYP science asks four different questions, and each one is a separate criterion with its own marks. A student who knows every fact in the periodic table but cannot design a fair test, process a set of results or weigh the consequences of an industrial process will lose three-quarters of the available credit. Criterion-based learning means studying each of these four skills deliberately, not hoping they develop by themselves.
A · Knowing and understanding
Recall and explain chemistry; use it to solve problems in familiar and unfamiliar situations; analyse information to reach a judgement supported by science.B · Inquiring and designing
Turn a question into something testable: a research question, a hypothesis with a scientific reason, the variables, and a method that someone else could follow to collect sufficient, valid data safely.C · Processing and evaluating
Present raw and processed data; interpret it with scientific reasoning; judge whether the hypothesis and the method are valid; suggest improvements and extensions.D · Reflecting on the impacts of science
Explain how chemistry is applied to a real problem; discuss and evaluate its environmental, economic, social and ethical implications; reach a supported conclusion using correct scientific language.The four criteria are not four separate subjects. They are four ways of using the same chemistry. Collision theory, for example, is criterion A when you explain why powdered coal burns faster than lumps; criterion B when you write “because the particles collide more frequently” in a hypothesis; criterion C when you explain why a smaller particle size gave a steeper graph; and criterion D when you argue about the cost and safety of grinding a raw material. The topic chapters are written so that every idea can be used in all four ways.
Criterion A asks what and why. Criterion B asks how would you find out? Criterion C asks what do these results show, and can you trust them? Criterion D asks so what — for people, the economy and the environment?
02 / The Year 5 criteria
Strands and achievement levelsYear 5 criteria
In school-based assessment each criterion is marked out of 8, using the Year 5 level descriptors of the MYP sciences guide. Each criterion is divided into strands — the separate things a student must show — and the level awarded depends on how far each strand is met.
| Criterion | At the end of Year 5, students should be able to… |
|---|---|
| A Knowing and understanding | i. explain scientific knowledge ii. apply scientific knowledge and understanding to solve problems set in familiar and unfamiliar situations iii. analyse and evaluate information to make scientifically supported judgments |
| B Inquiring and designing | i. explain a problem or question to be tested by a scientific investigation ii. formulate a testable hypothesis and explain it using scientific reasoning iii. explain how to manipulate the variables, and explain how data will be collected iv. design scientific investigations |
| C Processing and evaluating | i. present collected and transformed data ii. interpret data and explain results using scientific reasoning iii. evaluate the validity of a hypothesis based on the outcome of the scientific investigation iv. evaluate the validity of the method v. explain improvements or extensions to the method |
| D Reflecting on the impacts of science | i. explain the ways in which science is applied and used to address a specific problem or issue ii. discuss and evaluate the various implications of using science and its application to solve a specific problem or issue iii. apply scientific language effectively iv. document the work of others and sources of information used |
2.1 The command-term ladder
Read the level descriptors from bottom to top and a pattern appears: the same strand is described with a more demanding command term at each level. This is the single most useful idea in criterion-based learning, because it tells a student exactly how to move up a level — not by writing more, but by doing a harder kind of thinking.
| Strand | Levels 1–2 | Levels 3–4 | Levels 5–6 | Levels 7–8 |
|---|---|---|---|---|
| A i. scientific knowledge | state | outline | describe | explain |
| A ii. solving problems | suggest solutions (familiar) | solve (familiar) | solve familiar; suggest for unfamiliar | solve familiar and unfamiliar |
| A iii. judgments | interpret information | interpret → scientifically supported judgments | analyse | analyse and evaluate |
| B ii. hypothesis | outline a testable hypothesis | formulate, using scientific reasoning | formulate and explain | formulate and explain, using correct scientific reasoning |
| B iv. method | design, with limited success | safe method; select materials and equipment | complete and safe; appropriate equipment | logical, complete and safe |
| C iii–iv. validity | state | outline | discuss | evaluate |
| C v. improvements | state | outline | describe | explain |
| D ii. implications | outline | describe | discuss | discuss and evaluate |
To lift an answer one level, change its verb. A stated improvement (“use more trials”) becomes an explained one (“use at least three trials at each concentration and calculate a mean, so that one anomalous reading has less effect on the conclusion”). A described implication becomes an evaluated one when it is weighed against another and a judgement is made.
Three expectations in the guide deserve emphasis. For criterion A, the top level requires students to make scientifically supported judgments about the validity or quality of information presented to them — media claims, other people's results. For criterion B, the top level asks for a method that contains only the relevant information, correctly sequenced — length is not the goal. For criterion D, students reflect on the implications of science interacting with a factor — moral, ethical, social, economic, political, cultural or environmental — and document their sources.
Climb the ladder
Each answer below sits at one level of the ladder. Choose the command term it demonstrates.
03 / The on-screen examination
How the examination is builteAssessment structure
The MYP Year 5 chemistry examination is taken on screen and is marked out of 100. Every paper reviewed for this guide was organised into the same three tasks, each introduced with a key concept (relationships, change or systems):
| Task | Criteria assessed | Marks per paper | Typical content |
|---|---|---|---|
| Knowing and understanding | A | 21–28 | Short answers: periodic table positions, particle numbers, formulae, names, Lewis structures, balancing, mole calculations, explanations. |
| Investigation skills | B C | 46–54 | Research questions, hypotheses, variables, a long “design an investigation” answer, tables, graphs, means, validity, improvements. |
| Applying science | D | 22–27 | A real-world issue set in a global context; long “discuss and evaluate” answers using data from the stimulus. |
Two features of Table 1 matter for revision. First, the investigation-skills task carries about half of the marks, so practical reasoning is not an optional extra. Second, within each task individual parts can be credited to a different criterion. A calculation inside the investigation task may be marked as criterion A; a short “suggest a reason” inside the first task may be marked as criterion D. The criterion follows the skill being used, not the position of the question on the screen.
Examination feedback repeatedly makes the same practical point: students who have used the familiarisation materials and past tasks manage their time better, particularly on graph-drawing tools and drop-down selections. Several answers were lost simply because a drop-down was left showing “?”.
Grade boundaries are set after each session and move. In the three sessions for which reports were available, the lowest mark for a grade 4 ranged from 45 to 58 out of 100, and a grade 7 needed between 73 and 82. Treat any fixed “target mark” with caution.
04 / Command terms
Command terms decide the answerAll criteria
The command term tells you how much to write and what kind of thinking to show. Examination feedback singles out misunderstood command terms as a cause of lost marks in every recent session. The definitions below are those of the MYP sciences guide (the definition of compare is the general MYP one); the third column shows what the marking of past examination tasks rewarded.
| Term | Definition | Evidence from marking |
|---|---|---|
| State / Identify / Select | State: give a specific name, value or other brief answer without explanation or calculation. Identify: provide an answer from a number of possibilities. Select: choose from a list or group. | One mark per item. A contradiction (two answers) scores zero. |
| Outline | Give a brief account or summary. | Feedback: a bare statement that solar power releases no pollutant gases missed the comparison with fossil fuels that the second mark needed. |
| Describe | Give a detailed account or picture of a situation, event, pattern or process. | Credit goes to specific observations or steps, not general remarks. |
| Explain | Give a detailed account including reasons and causes. | Marks are usually split between the fact and the linked cause, e.g. “H atom has one electron” and “needs to share to reach a full shell”. |
| Calculate | Obtain a numerical answer showing the relevant stages in the working. | Separate marks for method, value, significant figures and unit are common. |
| Determine | Obtain the only possible answer. | Feedback: giving a range when asked to determine an optimum, or writing a whole equation when only the salt formula was asked for, did not earn the mark. |
| Suggest | Propose a solution, hypothesis or other possible answer. | Lists of “accept any reasonable” answers appear in the marking guidance. |
| Formulate (a hypothesis) | Express precisely and systematically the relevant concept(s) or argument(s). For a hypothesis: If… then… because… | Three marks: the change, the predicted effect, and the scientific reason. The because is where most marks are lost. |
| Design | Produce a plan, simulation or model. | Marked holistically in rows (see section 5). |
| Present | Offer for display, observation, examination or consideration. | Marks for title, labelled axes with units, even scale, correct plotting and graph type. |
| Interpret / Analyse | Interpret: use knowledge and understanding to recognize trends and draw conclusions from given information. Analyse: break down to bring out the essential elements or structure. | Answers must quote values from the table or graph. |
| Compare | Give an account of the similarities and differences, referring to both (all) of them throughout. | Feedback: students listed the properties of each fabric or process instead of comparing them. |
| Justify | Give valid reasons or evidence to support an answer or conclusion. | Usually a second mark that is only available if the choice is correct. |
| Discuss and evaluate | Discuss: offer a considered and balanced review including a range of arguments, with conclusions supported by evidence. Evaluate: make an appraisal by weighing up the strengths and limitations. | Marked in rows that match the bullet points, finishing with an appraisal that links the issues. |
Command-term check
Each item is an answer written by a student. Decide whether it meets the command term.
05 / Criterion A
Criterion A in practiceA Knowing and understanding
Criterion A is where the content of the seven topic chapters is tested directly. Three kinds of demand appear:
- Knowledge — recall a fact, name or definition (e.g. the meaning of isotope).
- Application — use knowledge in a context you have not seen (e.g. finding the number of neutrons in an element produced by nuclear fusion from a nuclear equation).
- Analysis — use information supplied in the task to reach a judgement (e.g. choosing which metal oxide is only present in one type of glass from a composition table).
Precision is what separates full from partial credit. A formula needs correct subscripts and brackets (Mg3(PO4)2 earns nothing without the brackets). A molar mass needs its unit. A mass given in kilograms has to be converted to grams before dividing by the molar mass; examination feedback describes answers that were exactly a factor of 1000 out for this reason in two separate sessions.
Some of the major components of gas-rich planets are helium (He), hydrogen (H2) and ammonia (NH3). Explain why hydrogen occurs as diatomic molecules, but helium does not.
Marking guidance and model answer
- 1A hydrogen atom has one electron in its outer shell.
- 1Hydrogen atoms need to share electrons to gain stability / to obtain the electron arrangement of a noble gas.
- 1Helium already has a full (complete) outer shell — “stable electron shell”, “noble gas configuration” or “complete duplet” are accepted.
- 1So helium has no need to share electrons / does not bond / is already stable.
Why answers lose marks: “balanced” is not accepted as a description of helium's shell. Each marking point is a link: fact about the atom → consequence for bonding. Two facts without the links earn only two marks.
- Formula: correct symbols, subscripts, brackets and charges.
- Calculation: working shown, value, significant figures as asked, unit.
- Explanation: every statement followed by its cause or consequence.
- Unfamiliar context: find the chemistry you know inside the story before you write.
06 / Criterion B
Criterion B: designing a fair testB Inquiring and designing
6.1 Research question and hypothesis
A good research question names the independent variable and the dependent variable and can be answered by measurement: How does the temperature of water affect the time taken for tea to diffuse completely? The hypothesis then predicts the answer and gives a reason from science:
If [change in IV] … then [predicted change in DV] … because [scientific reason].
The because must contain chemistry — particles, energy, collisions, bonding, reactivity — not a restatement of the prediction. “Because the tea diffuses faster” only repeats the then. “Because the particles have more kinetic energy, so they move and mix with the water molecules more quickly” is a reason. Examination feedback reports that most students write the If and then successfully but lose the because, often because they did not use information supplied in the stem of the question.
Teeth and bones contain calcium carbonate, which reacts with hydrochloric acid to give carbon dioxide. A scientist developed this research statement: “The higher the percentage of calcium carbonate in the bones or teeth, the larger the volume of carbon dioxide produced when reacted with acid.”
Identify the variables in this investigation: independent variable; dependent variable; control variable 1; control variable 2.
Marking guidance and model answer
- 1Independent: percentage of calcium carbonate or type of bone/tooth. (“Calcium” alone is not accepted.)
- 1Dependent: (volume of) carbon dioxide produced.
- 2Any two control variables, e.g. mass of bone/tooth; volume of acid; concentration of acid; temperature; surface area or size of bone.
Not accepted: “amount of bone” and “type of acid”. The word amount does not say what is measured. Always name the quantity: mass in g, volume in cm3, concentration in mol dm−3.
6.2 Variables
The independent variable (IV) is the one you choose and change. The dependent variable (DV) is the one you measure. Control variables (CV) are kept the same so that only the IV can affect the DV. Two errors recur in examination feedback. Students swap the IV and DV, and students give a DV that is calculated rather than measured. “Rate of reaction” is calculated; “volume of gas collected in 60 s” or “change in mass of the metal sample” is measured and can be put in a table.
Variable sorter
Investigation: which roofing material (five types) reacts least with hydrochloric acid? Classify each statement as a student might write it.
6.3 The design question
Every paper reviewed contained one long question beginning Design an investigation… or Design a method…, worth between 15 and 19 marks. These are marked holistically: the examiner reads the whole answer and awards a level (usually 1–4) for each row of a grid. The rows are the bullet points in the question. Across the papers reviewed the rows were drawn from this set:
| Row | What reached the top level |
|---|---|
| Variables | IV and DV identified correctly and two (sometimes more) control variables stated. |
| Equipment | Equipment to measure the DV and to control the named CVs (e.g. balance for mass of catalyst, measuring cylinder or pipette for volume of acid, stopwatch). |
| Method | Complete, fully explained, could be repeated by another student; states how each CV is controlled; states how the result (e.g. rate) is worked out from measured data. |
| Sufficient data | Every value of the IV tested (all five fuels, all six metals…), at least three trials each, and a mean calculated. |
| Safety | A precaution linked to a specific hazard of the chemicals used (corrosive acid, oxidising peroxide, flammable fuel). |
| Assumptions (some papers) | e.g. all the calcium carbonate reacted; temperature and pressure remained constant. |
| Justification of set-up (some papers) | Chosen apparatus justified: the temperature change can be measured and heat losses are minimised. |
Two points follow. A design answer written as one paragraph makes it easy to miss a row; using the bullet points as headings is the simplest way to cover them all, and examination feedback recommends exactly this. Secondly, “wear goggles” is only the lower level in the safety row: the top level needs the hazard — “hydrochloric acid is corrosive/irritant, so wear eye protection and wipe up spills immediately”.
Design answer self-check
Choose the statement that best describes your answer for each row. The levels summarise the grids used in past marking; exact wording varies between questions.
Metals react with acids but they do not all react at the same rate. You need to design a case for a battery that contains acid. You are provided with iron, zinc, lead, copper, tin and chromium, standard glassware, other laboratory equipment and sulfuric acid.
Design a method to determine which metal is most resistant to acid leaking from the battery. In your answer you should include:
- the independent, dependent and control variables
- details of how you will manipulate the variables
- a list of the equipment you will need
- details of the data you will collect
- how you will use your data to decide which metal is most resistant to the acid
- how you will ensure your method is safe.
Marking guidance and a top-band plan
The marks were awarded in bands. The top band (13–18) required: a correct, quantitative DV; metal as the IV; at least two control variables, justified and with details of control; complete equipment likely to generate quantitative data; a complete method another student could follow; a plan to repeat and calculate an average; and care with acids. Answers with only a qualitative DV (e.g. “see how many bubbles”) could not rise above the lowest band.
A plan that meets the top band
- IV: type of metal (all six). DV: loss in mass of the metal after 10 minutes in acid (g), or volume of hydrogen collected in a fixed time (cm3). CVs: volume and concentration of sulfuric acid; surface area/size of metal sample (cut to the same dimensions and cleaned with emery paper); temperature (water bath); time of immersion.
- Equipment: balance (±0.01 g), 50 cm3 measuring cylinder, boiling tubes and rack, stopwatch, thermometer and water bath, emery paper, tongs, paper towels.
- Method: clean and weigh each metal strip; add 20 cm3 of the same acid at 25 °C; leave for 10 minutes; remove, rinse, dry and reweigh; calculate loss in mass. Repeat three times for every metal with fresh acid and calculate the mean loss in mass.
- Decision: the metal with the smallest mean loss in mass is the most resistant.
- Safety: sulfuric acid is corrosive — wear eye protection and gloves; hydrogen produced is flammable — no flames nearby.
07 / Criterion C
Criterion C: data you can trustC Processing and evaluating
7.1 Tables
A results table has the IV in the first column and the DV in the following columns, one column per trial, then a column for the mean. Units go in the column headings, written quantity / unit (e.g. Volume of CO2 / cm3), and not beside every number. Marking guidance for table questions rewarded exactly these features: a column for the IV, a column for the DV, the unit, columns for repeats and a column for the average.
7.2 Graphs
The choice of graph depends on the IV. If the IV is categoric (type of fruit juice, brand of nappy, type of fuel) draw a bar chart. If the IV is continuous (temperature, altitude, concentration, time) draw a scatter graph and, where appropriate, a line of best fit. Examination feedback in recent sessions identified: missing units in axis labels; scales without equal increments; bar charts or histograms whose value axis did not start at zero; the IV plotted on the wrong axis; and difficulty drawing a line of best fit.
Choose the graph
Two data sets from past examination tasks. Choose a graph type for each and compare what the chart shows.
7.3 Processing: means, outliers and significant figures
A mean is calculated from repeat trials after removing any anomalous (outlying) result. The mean should be given to the same number of decimal places as the raw data, or to the number of significant figures asked for. Keep the unit.
Limestone was reacted with hydrochloric acid and the volume of CO2 recorded.
| Time / s | Trial 1 / cm3 | Trial 2 / cm3 | Trial 3 / cm3 | Average / cm3 |
|---|---|---|---|---|
| 30 | 46 | 48 | 44 | 46 |
| 40 | 57 | 67 | 55 | ? |
| 50 | 70 | 70 | 70 | 70 |
Analyse the data and determine an appropriate average volume of gas produced at a time of 40 seconds. Justify your answer.
Marking guidance
- 1Appropriate average = 56 cm3 (from 57 and 55).
- 1It is not appropriate to include an outlier (67 cm3) in the average.
An average of 60 cm3 (all three values) earned only one mark, and the justification mark was then withheld even if the reasoning was correct.
A student compared two fragranced candles of different mass.
| Vanilla candle | Mass / g | Burn time / hours | Strawberry candle | Mass / g | Burn time / hours |
|---|---|---|---|---|---|
| 1 | 185 | 29 | 1 | 114 | 32 |
| 2 | 185 | 24.3 | 2 | 114 | 28.5 |
| 3 | 185 | 28 | 3 | 114 | 29.5 |
| Average | 27.1 | Average | ? |
Marking guidance
(a) 130 hours 1expressed as 30.0 (three significant figures, matching the data).
(b) 1The friend left out the outlier (24.3 hours): (29 + 28) ÷ 2 = 28.5.
(c) 1Not valid, because the strawberry candle has the longer burn time; plus any two of: different containers; different masses so no direct comparison; insufficient data; the vanilla trials would need repeating because of the 24.3-hour result; different wick sizes.
(d) One improvement with its linked justification, e.g. use the same mass of wax / same container so that heat transfer is identical; or more trials and averages to reduce random error. More trials with different fragrances does not improve validity.
7.4 Validity, reliability and improvements
These words are used precisely. Data are reliable (consistent) when repeat trials agree closely. A method is valid when it measures what it claims to measure and only the IV is allowed to change. A hypothesis is valid (supported) when the processed data show the predicted trend. An estimate is more trustworthy by interpolation (inside the range of data) than by extrapolation (outside it).
More trials improve reliability — they reduce the effect of random error. They do not fix a method that measures the wrong thing. Examination feedback describes a task where most students suggested more trials when the missing step was that pH had not been measured at all. Ask: is the method measuring the right quantity, with the other variables controlled? before suggesting repeats.
“Human error” earns nothing. Name the specific error and its direction: “the stopper was not inserted, so gas escaped and the volume collected was too low”.
A graph was drawn of the percentage charge kept by a lithium-ion battery against storage temperature for data collected between 0 °C and 60 °C. The graph was used to estimate the charge kept at 50 °C and at 80 °C. Compare the validity of the two estimations.
Marking guidance
- 1The estimate at 50 °C is valid because it lies within the data set (interpolation).
- 1The estimate at 80 °C may be invalid because it lies outside the data set (extrapolation).
08 / Criterion D
Criterion D: science in the worldD Reflecting on the impacts of science
The applying-science task gives a real problem — oil spills, copper in waste water, desalination, radioactive waste, fast fashion — with a global context and a set of information in text, tables, infographics or video. The long answer asks you to discuss and evaluate, and its bullet points become the rows of the marking grid. A typical grid for a two- or three-option problem contains rows for the science (how each option works or how efficient it is), environmental impact, economic impact, social or ethical impact, and a concluding appraisal.
8.1 Compare, do not list
The most frequent weakness named in examination feedback is listing. Copying three bullet points about each option from the stimulus is not a comparison. A comparison puts the two options side by side on the same criterion and uses the data: “Chemisorption removes more than 99 % of copper ions at low concentration, while precipitation removes most of the metal even at high concentration, so precipitation suits the concentrated waste from circuit-board etching.”
8.2 Supported by science
The top level of a row usually needs the point to be supported by scientific reasoning. “Burning the oil causes pollution” is a statement; “burning removes the oil but releases smoke and carbon dioxide from incomplete and complete combustion of the hydrocarbons” is supported by chemistry.
8.3 A conclusion that links the issues
The final row rewards an appraisal that links the issues discussed — not a new idea and not a one-word choice. Weigh them: “Although electrochemical recovery has high set-up and energy costs, it produces no waste sludge and recovers pure copper that can be sold, so over the lifetime of the factory it best meets the green chemistry principle of preventing waste.” When the question says choose one option (“sea dumping or underground storage”), answer about one option only.
A family uses water from a private well. The table shows contaminants that may be present, and two home filtration units.
| Contaminant | Size / µm | Effect |
|---|---|---|
| E. coli (bacteria) | 0.5–2 | diarrhoea, infections |
| Giardia (parasite) | 4–6 | diarrhoea, cramping |
| Hepatitis A (virus) | 0.055–0.065 | liver disease |
| Heavy metals | <0.001 | liver/kidney damage |
| Nitrates | <0.005 | reduce oxygen carried by blood |
| Ceramic core unit | Activated carbon unit | |
|---|---|---|
| Cost of unit / US$ | 166.00 | 92.00 |
| Cost of filters / US$ | 67 | 26 |
| Filter life span / months | 12 | 6 |
| Water flow / dm3 min−1 | 1.8–3.8 | 1.2–2.5 |
| Filter pore size / µm | 0.22 | 0.6 |
| Operating temperature / °C | 5–30 | −1 to 51 |
Marking guidance and model answer
(a) Pore size; the pores of the filter need to be smaller than the material being separated out.
(b) Marked in two rows. Advantages and disadvantages (up to 4): an advantage and a disadvantage of the ceramic unit (or the reverse argument), with the top level needing both supported by scientific reasoning. Justification (up to 2): a simple justification, then one with supporting evidence.
Model answer. The ceramic unit's pores (0.22 µm) are smaller than the smallest E. coli (0.5 µm) and Giardia (4 µm), so both are trapped; the carbon unit's 0.6 µm pores could let the smallest bacteria through. Neither filter's pores are small enough to stop hepatitis A viruses, heavy-metal ions or nitrate ions by size. The ceramic unit also has the higher flow rate. Its disadvantages are cost — US$166 against US$92, with filters costing US$67 a year compared with US$52 a year (two at US$26) — and a narrower operating temperature range. Because the main risk from a well contaminated by sewage is bacteria and parasites, the ceramic unit is more suitable: the extra cost buys a filter whose pores are smaller than the organisms that cause disease.
Printed circuit boards are made using a copper layer; unwanted copper is removed by a chemical reaction, leaving a waste solution of copper ions that must be treated before the water is returned to the water supply (copper ions may cause liver damage and insomnia). Four treatment processes are summarised:
| Precipitation | Electrochemical recovery | Chemisorption | Photocatalysis |
|---|---|---|---|
| Simple and safe; inexpensive; removes most of the metal even at high copper concentration; large amount of waste sludge with disposal problems; large volume of additional chemicals. | Particular metals removed; pure metal obtained; high set-up cost; electrodes replaced; high energy use; no additional chemicals; no waste products. | Removes >99 % of ions at low concentration; not efficient at high concentration; some adsorbents reusable; high initial cost; copper can sometimes be recovered; minimal waste. | New, experimental; uses solar energy; removes 100 % of copper ions; needs more than a week; large area needed for UV activation; cheap catalyst. |
You are setting up a new circuit-board factory in an area where copper in the water supply has already caused illness. Discuss and evaluate two processes. Consider: efficiency; environmental impact; economic impact; how each matches the green chemistry principles (preventing waste, energy efficiency, renewable raw materials); complexity; your final choice with justification.
Marking guidance and how to plan the answer
The grid had six rows matching the bullets: Efficiency (to 4: both methods compared with scientific justification); Environmental impact (to 3: both methods with scientific reasoning); Economic impact (to 2: both methods); Green chemistry (to 2: two principles); Complexity (to 4: both methods compared with justification); Final choice (to 2: choice with justification).
Planning grid. Draw a table with the two chosen processes as columns and the six bullets as rows before writing. Fill every cell with a point from the stimulus plus a “so…” that explains its consequence. Then write the paragraphs across the rows — comparing — rather than down the columns. Finish with a choice that weighs the most important row for this community (removing copper completely and quickly, because people are already ill).
Steel is the world's most recycled material. Outline how greater use of the three Rs of sustainability (reduce, reuse, recycle) could reduce the use of natural resources and benefit the wider global community.
Marking guidance
Any four reasonable points, for example: conserving finite raw materials; conserving natural resources (for other uses); reduction in CO2 emissions / climate change; reduction in waste as products are recycled; reduction in waste material associated with mining; reduced destruction of environments and habitats.
09 / Examination feedback
Examiner's overall observationAll criteria
Examiner's overall observation
Generally well done. Balancing equations; identifying groups and periods; the effect of catalysts on activation energy; writing a research question from given variables; forming the If and then of a hypothesis; identifying variables and designing a method; plotting data with suitable labels; evaluating given information; calculating molar masses and Rf values when distances were supplied.
Persistent difficulties. Using the because of a hypothesis to give a scientific reason; swapping independent and dependent variables; using the word amount instead of mass or volume; giving a calculated quantity (rate) as the dependent variable; forgetting at least three repeats and a mean; linking safety to a specific hazard; recognising the toxic hazard symbol; units on axis labels; equal scale increments and starting bar charts at zero; interpreting graphs with negative values; distinguishing qualitative from quantitative data; knowing that more trials do not increase validity; attributing anomalies to “human error”; converting kg to g and m to µm in stepwise fashion; standard form and significant figures.
Criterion D. Students identified impacts on the environment, economy and individuals well, but many listed information rather than comparing options, omitted data from the stimulus, answered about both options when asked for one, or gave conclusions without justification.
What successful answers showed. They used the bullet points as a framework, quoted values from the stimulus, followed every statement with its scientific cause, and ended with a conclusion that weighed the issues already discussed.
10 / Revision
Criteria knowledge organiserSummary
A Knowing and understanding
- Formula precision: subscripts, brackets, charges
- Units on every calculated answer
- kg → g (× 1000) before n = m / M
- Explain = fact + cause/consequence
- Unfamiliar context: find the familiar chemistry
B Inquiring and designing
- RQ names IV and DV
- If … then … because [science]
- DV is measured, not calculated
- Never write “amount”
- All IV values × 3 trials + mean
- Safety linked to a named hazard
- Use the bullets as headings
C Processing and evaluating
- Table: IV | trials | mean; units in headings
- Categoric IV → bar chart; continuous → scatter + best-fit line
- Title links IV and DV; axes labelled with units; even scale
- Remove outliers before averaging
- Reliable = consistent; valid = measures the right thing fairly
- Interpolation > extrapolation
- Name specific errors and their direction
D Reflecting on impacts
- Compare side by side; do not list
- Quote data from the stimulus
- Support each point with chemistry
- Environmental · economic · social · ethical
- Conclusion weighs and links the issues
- Answer the option asked for
Other chapters: Criteria A–D · 1 · Periodic table · 2 · IUPAC naming · 3 · Atmosphere · 4 · Matter · 5 · Pure and impure · 6 · Bonding · 7 · Types of reaction
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