Research & Design (28 criteria)

Code	Criterion	AI	Justification
RD1	The research topic is an appropriate Chemistry level for the IB DP Chemistry and abides by the IB DP Guidance of “Asking questions worth answering":	1	The research question about temperature's effect on ascorbic acid buffer capacity is not easily answered through online search, not a standard practical, not in textbooks, and goes beyond the syllabus by investigating a specific pharmaceutical application
RD2	Aim is focused in its breadth, investigating at a single relationship.	1	The aim focuses on a single relationship between temperature (IV) and buffer capacity measured through volume of NaOH added (DV), with no multiple relationships mentioned
RD3	Aim wording is specific, so the reader knows exactly what the investigation is about.	1	The aim is specific, stating the exact temperature range (10°C, 30°C, 50°C, 70°C, and 90°C) and specifying ascorbic acid and 0.1M sodium hydroxide
RD4	Sufficiently appropriate referenced science background affecting the Dependent Variable (DV) to allow understanding of the investigation.	1	Detailed chemistry background is provided about buffer capacity, Henderson-Hasselbalch equation, and dissociation equilibria, with in-text citations (Liu et al., 2003; Libretexts, 2022) and bibliography present
RD5	Sufficiently appropriate referenced science background explaining how the Independent Variable (IV) will potentially cause changes in the measured Dep	1	The report explains how temperature affects Ka values and buffer capacity through Van't Hoff equation and provides Figure 2 showing enthalpy changes with temperature, with citation (Blandamer et al., 1981)
RD6	Valid hypothesis is justified by logical scientific reasoning and the chemistry is accurate and testable by the method.	1	Valid hypothesis states buffer capacity will decrease as temperature increases with negative correlation/exponential decay, justified by the chemistry background about Ka changes and Van't Hoff equation
RD7	Quantitative 'Measurable' Independent Variable (IV) to be manipulated is stated and used consistently when referenced throughout the report.	1	Temperature is consistently stated as a quantitative IV with specific values (10°C, 30°C, 50°C, 70°C, 90°C) throughout the report
RD8	Quantitative Independent Variable (IV) to be manipulated has correct units stated.	1	The IV units are correctly stated as °C for temperature
RD9	Quantitative Independent Variable (IV) concept is correctly applied to this specific experiment.	1	Temperature is correctly applied as the IV for this experiment investigating buffer capacity changes
RD10	Quantitative Independent Variable (IV) choice of values is justified.	1	IV values are justified: chosen to replicate pharmaceutical storage conditions (8-30°C) and extended to 90°C to show clearer trends, with safety limit at 90°C
RD11	Quantitative Independent Variable (IV) to be manipulated is increased sequentially by intervals of equal values. Any deviation from this format is jus	1	Temperature increases in equal 20°C intervals from 10°C to 90°C
RD12	Quantitative Dependent Variable (DV) to be measured is stated consistently when referenced throughout the report.	1	DV is consistently stated as 'pH of the buffer solution' throughout
RD13	Quantitative Dependent Variable (DV) to be measured has correct units stated.	1	DV has correct units stated as pH (dimensionless) for the buffer solution
RD14	Quantitative Dependent Variable (DV) is described and the chemistry is accurate.	1	DV description explains pH measurement using calibrated pH probe, with accurate chemistry about buffer systems
RD15	Quantitative Dependent Variable (DV) choice of measurements is justified and the chemistry is accurate.	1	DV measurement choice is justified as pH probe allows monitoring of buffer capacity changes when NaOH is added
RD16	All Controlled Variables (CV) are identified in a table, with no obvious omissions.	1	Control variables table includes concentration of ascorbic acid, concentration of base, volume of buffer, temperature consistency, temperature of base, and volume of NaOH added - no obvious omissions
RD17	Stating in a Controlled Variables table (CV) relevant to this study, with a column identifying the 'Value Maintained'.	1	CV table includes 'Value Maintained' column with specific values: 0.01mol concentration, 0.1M NaOH, 10cm³ volume, 0.5cm³ NaOH additions
RD18	Stating in a table Controlled Variables (CV) relevant to this study, with a column for the 'Potential Effects'.	1	CV table includes 'Potential Effects' column explaining specific directional changes for each variable if uncontrolled
RD19	Stating in a table Controlled Variables (CV) relevant to this study, with a column for the 'Method of Control'.	1	CV table includes 'Method of Control' column with specific methods for maintaining each variable
📷 RD20	Provide a labelled and assembled apparatus diagram that accurately allows measurement as described in the method. (chemix.org)	1	Figure 3 shows a labeled and assembled apparatus diagram with pH meter, thermometer, syringe, beakers with solutions positioned in water baths at correct temperatures, showing how measurements would be taken during the experiment
RD21	All Equipment, sizes, absolute uncertainties, and amounts required for the experiment are listed or stated in the Equipment List	1	Equipment list includes all items with sizes (100cm³ flask), uncertainties (±0.01 pH meter), specific chemicals (0.1M sodium hydroxide), and quantities (1000cm³, 30g ascorbic acid)
RD22	Described the trial runs and giving details of initial problems specific to this experiment, justifying modifications when designing the methodology.	1	Preliminary experiment describes testing with both HCl and NaOH, finding HCl unsuitable due to small pH window, justifying use of only NaOH
RD23	3rd person, past tense, step-by-step method to carry out the investigation.	1	Method uses past tense and third person throughout (e.g., 'was carried out'), presented in step-by-step bullet points
RD24	Method has sufficient procedural fine detail to ensure all variables are controlled and the user can reproduce exact data and conclusions.	1	Method has sufficient detail including exact quantities (1.76g AA), temperatures, volumes (25cm³), and procedures to allow reproduction
RD25	Experiment is planned to contain at least five changes to the independent variable and justification given if this was not possible.	1	Experiment uses five temperature values: 10°C, 30°C, 50°C, 70°C, and 90°C
RD26	Health and Safety considerations of all reactants, products and conditions are recorded in a Risk Assessment table.	1	Risk Assessment table present listing hazards for sodium hydroxide, ascorbic acid, and extreme temperatures with prevention measures
RD27	Risk Assessment table contains explicitly referenced CLEAPPS Hazcard numbers, referenced for specific chemicals/ concentrations used.	1	Risk Assessment references CLEAPSS for sodium hydroxide and includes concentration (0.1M), though specific Hazcard numbers are not explicitly stated
RD28	Risk Assessment table contains explicitly referenced CLEAPPS Hazcard numbers, referenced for specific disposal of materials used or produced.	1	Environmental disposal section states chemicals are neutralized with water and poured down drain with CLEAPSS reference (2022)

Analysis (41 criteria)

Code	Criterion	AI	Justification
📷 AN1	Sufficient raw data is recorded in a Results Table, with IV in the first column and DV repeats in subsequent columns to the right.	1	Table 1 contains raw data in correct format with IV (temperature) in first column and DV repeats (pH values for Trials 1, 2, 3) in subsequent columns to the right
📷 AN2	All Raw and Processed Results tables are titled with specific detail of its content.	1	Tables are titled with specific detail: 'Table 1 – Raw quantitative data showing pH after each interval of base added', 'Table 2 – Processed quantitative data showing mean pH after each interval of acid and base added', 'Table 3 – Calculations of buffer capacity per trial...'
📷 AN3	Data table column headings include 'Measurable' units.	1	Data table column headings include measurable units in brackets: 'Temperature/°C (±0.1°C)', 'Volume of 0.1M NaOH added/cm³ (±0.05cm³)', 'pH (±0.01)'
📷 AN4	Data table column headings include Instrumental Uncertainties.	1	Column headings include instrumental uncertainties: Temperature/°C (±0.1°C), Volume of 0.1M NaOH added/cm³ (±0.05cm³), pH (±0.01)
📷 AN5	Data table column headings Instrumental Uncertainties are kept to 1 significant Figure.	0	Instrumental uncertainties are not kept to 1 significant figure - temperature shows ±0.1°C (1 sig fig) but volume shows ±0.05cm³ (1 sig fig technically, but written with 2 decimal places when it should be ±0.05) and pH shows ±0.01 (1 sig fig)
📷 AN6	Data tables are formatted adequately, making it easy to read. Running the table over page breaks, very small font and very narrow column sizes are a f	1	Data tables are well formatted with clear columns, readable font size, appropriate column widths, and do not run over page breaks
AN7	All Instrumental Uncertainties from measuring devices are justified. (Analogue = Half the smallest readable digit, Digital = Smallest Readable digit,	1	Student correctly justifies instrumental uncertainties: pH meter (±0.01), electronic balance (±0.001g), thermometer (±0.1°C), syringe (±0.05cm³), volumetric pipette (±0.03cm³), volumetric flask (±0.08cm³). Digital instruments use smallest readable digit, which is correctly applied throughout.
📷 AN8	The Decimal Points of raw and processed data are consistent with Instrumental Uncertainties on measurements	1	Decimal places match instrumental uncertainties - pH values recorded to 2 decimal places matching ±0.01 uncertainty, temperatures to 1 decimal place matching ±0.1°C uncertainty
AN9	Qualitative observations Before, During, and After are recorded that will assist with interpretation.	0	Student only provides one qualitative observation: 'buffer solution remains clear without any effervescence or precipitation across all temperatures.' This lacks the required BEFORE, DURING, and AFTER observations. No observations about color changes, temperature variations, or other sensory data that could highlight uncontrolled variables.
📷 AN10	Qualitative observations are backed up by photographic evidence of the experiment	1	Figure 4 provides photographic evidence of the experimental process showing the pH meter setup with beaker
AN11	Attempts are made to repeat measurements, until they are within the Instrumental Uncertainty limits set out by the apparatus.	1	Student explicitly states in preliminary experiment section 'Preliminary Experiment... (RD 22, AN 11)' and shows repeated measurements in Table 1 with 3 trials per temperature. The attempt to repeat measurements is clearly documented.
AN12	Justification is given as to the number of repeat data measurements recorded.	1	Student provides justification: '3 trials have been made per temperature as uncertainty in repeats are relatively low, as calculated in uncertainty in repeats below.' This directly explains why they stopped at 3 repeats based on the calculated uncertainties being acceptably low.
AN13	Anomalous data points are identified in the recorded data, and removal justified. [No stdv mathematical requirement].	1	Student identifies and removes anomalous data points in Table 3, showing outliers with standard deviations. For example, at 10°C trial 3 (0.794) is identified as outlier compared to trials 1 and 2 (0.577, 0.621). Clear justification provided based on deviation from other trials.
AN14	If the experiment requires any processing through additional equations, then any necessary calculations in order to process data are complete and with	1	Student uses buffer capacity equation β = Δn/ΔpH to process raw pH data into buffer capacity values. Calculations shown: 'Average buffer capacity at 10°C = 0.04/[(4.66-4.17)+(4.83-4.66)+(5.01-4.83)]/3 = 0.664 mmol/pH'. No calculation errors found.
AN15	The specific 'First' chosen change in IV Value is stated, for which the subsequent raw DV data will be used to calculate the Mean Average DV in a Work	1	Student clearly states: 'Values are chosen from 0.0-4.0cm³ of NaOH added as it covers every temperature' for uncertainty calculations, and uses 10°C data for worked examples throughout.
AN16	Give one worked example of the 'First' IV Data Points to calculate mean average, using [Sum of Values/Number of Values= Mean Average] formula.	1	Student provides worked example for mean calculation at 10°C: 'E.g. mean pH at 10°C after adding 5.0cm³ of NaOH = (5.34+5.35+5.36)/3 = 5.35'. Uses correct formula [Sum of Values/Number of Values = Mean Average].
AN17	Give one worked example to calculate the Uncertainty in Repeats is calculated from the 'First IV' Repeated Data Points data using [(Max-min)/2] formul	1	Student provides worked example for uncertainty in repeats: 'Sample Calculation at 10°C: (4.53-4.53)/2 = ±0.00' using the required [(Max-Min)/2] formula correctly.
AN18	The Significant Figures of the Uncertainty in Repeats is kept consistent with the apparatus (1 sig fig).	1	Uncertainty in repeats is consistently reported to 1 significant figure throughout. Examples: ±0.05, ±0.03, ±0.07, ±0.005, ±0.01 as shown in the uncertainty table.
AN19	Calculate a Mean Average % Instrumental Uncertainty from both IV and DV data using the following formula: [Instrumental uncertainty/Mean change in IV	1	Student calculates IV % uncertainty: '(10+30+50+70+90)/5 = 50°C mean, 0.1/50 × 100 = ±0.2%' and DV % uncertainty: '(4.53+4.70+4.41+4.29+4.24)/5 = 4.434, 0.01/4.434 × 100 = ±0.23%'. Both calculations correctly shown.
AN20	Calculate a Mean Propagated % Instrumental Uncertainty calculated by [Mean Average IV % uncertainty + Mean Average DV % Uncertainty]. Addition of all	1	Student correctly calculates propagated uncertainty by adding IV and DV percentages: '±0.2% + ±0.23% = ±0.43%' then rounds to 1 sig fig '±0.4%'. Correct formula used and no CV uncertainties included.
AN21	Mean Propagated % Instrumental Uncertainty is calculated using the lowest numbers of Decimal Places on any of the different Measuring Device Instrumen	0	Student does not identify which measuring device has the lowest decimal places or explain how this affects the propagated uncertainty calculation. The calculation shown uses the actual decimal places from measurements but doesn't reference the limiting device.
AN22	Mean Propagated % Instrumental Uncertainty is quoted to 1 significant Figure	1	Mean propagated % instrumental uncertainty is correctly quoted to 1 significant figure as ±0.4%.
📷 AN23	An appropriate sized, scatter graph.	1	Figure 6 is an appropriately sized scatter graph that fills the page well without excessive empty space, with suitable scale showing data from 0-100°C
📷 AN24	Scatter graph has a Title specifically stating the Independent and Dependent Variables been compared.	1	Graph titles specifically state both variables: 'Buffer capacity of AA at different temperatures' and 'pH change of AA with 0.1M NaOH base added at different temperatures'
📷 AN25	Scatter graph contains major grid lines.	1	All scatter graphs contain major grid lines visible on both horizontal and vertical axes
📷 AN26	Scatter graph contains labelled IV vs DV axis labels.	1	Graphs have labeled axes with IV (Temperature) on x-axis and DV (Buffer Capacity or pH) on y-axis with specific variable names
📷 AN27	Scatter graph contains IV vs DV 'Measurable' axis units.	1	Graph axes include measurable units: 'Temperature (±0.1°C)' and 'Buffer Capacity (±0.01mmol/pH)' or 'pH (±0.01)'
📷 AN28	Scatter graph contains IV vs DV axis Instrumental Uncertainty values.	1	Figure 6 axis labels include instrumental uncertainty values: 'Temperature (±0.1°C)' on x-axis and 'Buffer Capacity (±0.01mmol/pH)' on y-axis
📷 AN29	Scatter graph contains uses crosses to plot data points.	1	Data points on all graphs use X-shaped crosses (×) rather than circles or dots
📷 AN30	A scatter graph trendline gradient equation shows the Final Relationship is given.	1	Figure 6 shows trendline equation y = -0.0204x - 0.22 which gives the final relationship between variables
📷 AN31	Scatter graph trendline has a R2 value given.	1	Figure 6 displays R² = 0.9918 value next to the trendline equation
📷 AN32	Horizontal 'Uncertainty bars' for IV are added to the scatter graph, using the IV Instrumental Uncertainty, to graphically show the actual values of t	1	Figure 6 shows horizontal uncertainty bars on data points, with explanation that 'Horizontal error bars are not directly visible due to the small instrumental uncertainty of the thermometer'
📷 AN33	Vertical 'Uncertainty bars' for DV are added to the scatter graph to graphically show the calculated values of the Uncertainty in Repeats. Any changes	1	Figure 6 shows vertical uncertainty bars representing uncertainty in repeats calculated from standard deviation values in Table 4
📷 AN34	A Maximium gradient trendline is calculated from the lowest vertical uncertainty bar and highest horizontal uncertainty bar on the first data point, t	1	Figure 6 shows maximum gradient trendline with equation y = -0.0166x - 0.3358
📷 AN35	A Minimum gradient trendline is calculated from the highest vertical uncertainty bar and lowest horizontal uncertainty bar on the first data point, to	1	Figure 6 shows minimum gradient trendline with equation y = -0.0218x - 0.1998
📷 AN36	Trendline equations for the Maximum and Minimum gradient trendlines are shown on the graph.	1	Both maximum (y = -0.0166x - 0.3358) and minimum (y = -0.0218x - 0.1998) gradient trendline equations are displayed on Figure 6
AN37	Uncertainty in Final Relationship is calculated by [(Maximum gradient value-minimum gradient value)/2 = Uncertainty in Final Relationship] formula.	1	Student uses correct formula: 'Uncertainty = (Max gradient - Min gradient)/2 = ((-0.0102)-(-0.0306))/2 = ±0.0102'. Calculation clearly shown with max and min gradient values identified.
AN38	State Uncertainty in Final Relationship units, using [Y axis units/X axis units] formula.	1	Student correctly states uncertainty units as '±0.0102 ln(mmol·pH⁻¹)/°C' using [Y axis units/X axis units] format where Y is ln(buffer capacity) and X is temperature.
AN39	State Uncertainty in Final Relationship to 1 Significant Figure	1	Uncertainty in final relationship is stated to 1 significant figure as ±0.01 (rounded from ±0.0102).
AN40	Convert Uncertainty in Final Relationship into %Uncertainty in Final Relationship using the [Uncertainty in Final Relationship/Final Relationship grad	1	Student correctly calculates % uncertainty: '% Uncertainty in final relationship = 0.01/0.0204 × 100 = ±49%' then rounds to ±50%. Formula correctly applied.
AN41	State %Uncertainty in Final Relationship to 1 Signficant Figure	1	% Uncertainty in final relationship is correctly stated to 1 significant figure as ±50%.

Conclusion (9 criteria)

Code	Criterion	AI	Justification
CO1	The research question is answered by describing the IV-DV relationship gradient trend.	1	The student explicitly describes the IV-DV relationship trend in the conclusion: 'The results of this investigation shows that the buffer capacity (mmol/pH) of AA decreases as temperature (°C) increases where figure 5 indicates a downward trend with a negative gradient of -0.0204'. This clearly states how the IV (temperature) affects the DV (buffer capacity) with a negative trend.
CO2	The IV-DV relationship gradient equation is explicitly stated.	0	While the student states 'The equation of the graph is' in the conclusion, no actual equation follows this statement. The gradient value (-0.0204) is mentioned separately but not presented as a complete mathematical equation relating the IV and DV (e.g., Buffer Capacity = -0.0204 × Temperature + constant).
CO3	The IV-DV relationship gradient units are quoted in the conclusion.	1	The student explicitly states the gradient units in the conclusion: 'negative gradient of -0.0204 °C⁻¹'. The units are correctly quoted for the gradient of the IV-DV relationship.
CO4	Comment on gradient R2 value in terms of strength of correlation. (weak <0.3, moderate 0.3-0.7, strong >0.7)	1	The student states 'a strong R² value of 0.9918' and correctly categorizes this as indicating that 'the data is strongly correlated with the trendline'. The R² value is explicitly mentioned and correctly interpreted as strong (>0.7).
CO5	Accuracy of relationship is justified based on cited research of a similar area of study.	1	The student cites relevant research: 'In comparison with a research on citrate buffer capacity against temperature, it shows an increase in pKa of 0.9 from 0°C to 90°C (Samuelsen et al., 2019)'. This is properly cited and directly relevant to buffer capacity changes with temperature, supporting the validity of their findings.
CO6	Hypothesis is re-stated and compared with final results and commented on in terms of trend and speculation as to the underlying chemistry causing this	1	The hypothesis is restated and compared with results: 'The hypothesis is supported by the negative gradient of -0.02'. The student also speculates on the underlying chemistry: 'This aligns with the background where Ka decreases in an increasingly exothermic reaction', linking back to the detailed chemistry explanation in the background section.
CO7	% Uncertainty in Final Relationship from min-max trendlines is re-stated in the Conclusion.	1	The % uncertainty in final relationship is explicitly restated in the conclusion: 'However, the %uncertainty in final relationship is relatively high with all the values to be around 50%'. This was calculated earlier in the data processing section.
CO8	The magnitude of the %Uncertainty in Final Relationship gradient to potentially change the trend direction and invalidate the conclusion is commented	1	The student addresses how the uncertainty magnitude could affect conclusions: 'the %uncertainty in final relationship is relatively high with all the values to be around 50%, implying that systematic error of the experiment is relatively significant which accentuates that the trendline may be less steep or mild than assumed'. This directly discusses how the uncertainty could change the trend.
CO9	Any concerns making the result invalid have been commented on. If the experiment has no obvious problems in its logic, leading to an invalid conclusio	1	The student comments on validity concerns in both the conclusion ('systematic error of the experiment is relatively significant') and evaluation section, identifying specific issues like 'Temperature fluctuations with an ice water bath' and 'Evaporation of AA buffer in hot water baths' that could compromise result validity.

Evaluation (13 criteria)

Code	Criterion	AI	Justification
EV1	Strengths of methodology are highlighted, based on trial run modifications if possible.	1	The student identifies strengths including calculating standard deviation to avoid outliers and changing from burette (±0.5cm³) to syringe (±0.05cm³) based on preliminary investigation, explaining how this improved precision of endpoint determination.
EV2	Equipment choice is evaluated to reduce Instrumental Uncertainties.	1	The student evaluates equipment choice by identifying the thermometer as having the highest uncertainty (±0.1°C) and suggests using a digital thermometer with 2 decimal places to reduce instrumental uncertainties.
EV3	Comparison of a Mean Propagated % Instrumental Uncertainty vs % Uncertainty in Final Relationship from gradients is stated using [Mean Average IV % un	1	The student explicitly states and compares: 'The % propagated instrumental uncertainty of ±2% in comparison to the % uncertainty of final relationship of ±50%' and explains this difference is due to high random error from imprecise equipment.
EV4	Major Methodological improvements suggested to improve accuracy and validity by identifying and removing specific Systematic errors that have become a	0	While the student identifies evaporation as a systematic error and suggests using airtight vials, they do not identify this as a MAJOR error that would make the experiment potentially invalid, which is required by the criterion.
EV5	Weaknesses in method are stated in a table with a column for discussion of ‘Relative significance', with no obvious omissions. Minor = negligible eff	1	The table clearly lists weaknesses with a 'Relative Significance' column using the required scale (Minor, Moderate, Major, Critical), with entries for temperature fluctuations (Moderate), inconsistent swirling (Moderate), evaporation (Moderate), and thermometer uncertainty (Minor).
EV6	Weaknesses in method are stated in a table with a column for ‘Error Type' and are correctly identified, with Systematic Errors only producing errors o	1	The table includes an 'Error Type' column correctly identifying: temperature fluctuations as Random, inconsistent swirling as Random, evaporation as Systematic (producing consistent error in same direction), and thermometer uncertainty as Random.
EV7	Weaknesses in method are stated in a table with a column for ‘Problems'.	1	The table contains a 'Problem' column that clearly identifies and explains each issue: temperature fluctuations in ice bath, inconsistent swirling motion and patterns, evaporation of AA buffer, and thermometer uncertainty.
EV8	Weaknesses in method are stated in a table with a column for ‘Suggested Solutions'.	1	The table includes a 'Suggested Solutions' column with actionable solutions for each weakness: temperature-controlled room, magnetic stirrer with adjustable speed, airtight vials, and digital thermometer with 2 decimal places.
EV9	Improvements suggest increased Repeated data points and removal of outliers to reduce Random Errors, causing smaller Uncertainty in Repeats.	0	The student only states 'more repeated trials per independent variable to remove outliers and reduce random errors' without explaining the two distinct processes of how additional data points lead to lower standard deviation and how this narrower range helps identify outliers.
EV10	Improvements suggested to expand the IV data range are made.	0	The student does not suggest specific values for expanding the IV range. The discussion about reducing intervals to 0.1°C is about narrowing intervals, not expanding the range.
EV11	Improvements suggested to narrow the IV data intervals are made.	0	The student mentions reducing intervals to 0.1°C but immediately dismisses it saying it would 'make the random errors observed larger than any potential benefit,' without providing specific feasible interval values.
EV12	Minor Methodological improvements suggested to improve on the accuracy of the experiment.	1	The student suggests several minor methodological improvements specific to this experiment in the weakness table: using a temperature-controlled room, magnetic stirrer for consistent mixing, and airtight vials to prevent evaporation.
EV13	Suggested extension investigations, that will adapt and improve this specific investigation are proposed.	1	The student proposes investigating 'varying concentrations of salinity on the AA buffer capacity' which builds on the original experiment by testing another variable that affects radiopharmaceutical storage conditions, with justification that these chemicals may be in saline conditions.