IB Biology SL Extended Essay Example

The question is measurable, but it is overloaded with two independent variables and several product-specific details. Because the mouthwash brands differ, the investigation cannot isolate fluoride concentration alone. The student should narrow the wording or redesign the method so only one factor changes at a time.

The title clearly signals the biological focus and the intended outcome of the investigation. This helps frame the report from the outset and gives the reader an immediate sense of the topic being studied.

The introduction shows a clear personal rationale and links the topic to a real-world health concern. That relevance improves focus because the reader can see why the investigation matters beyond the laboratory.

This background is generally clear, but the claim that enamel “prevents” damage is too absolute. A stronger explanation would note that enamel reduces risk but can still demineralize under prolonged acid exposure, which would make the later discussion of erosion more precise.

The justification overstates the equivalence between eggshell and enamel. Eggshell is calcium carbonate, while enamel is hydroxyapatite, so the model can only approximate acid dissolution rather than directly represent remineralization in teeth. The student should acknowledge this limitation explicitly in the rationale.

What assumption is being made here about the composition and purity of the eggshell, and how might that affect the claim that the acid volume was stoichiometrically sufficient in every trial?

This contains a scientific terminology error: eggshells are not from “oviparity mammals.” The student should use accurate biological language here and, if necessary, simply state that different bird eggshells can vary in thickness and composition.

The student gives a clear scientific definition and immediately ties it to the relevance of pH. This supports understanding because the mechanism is explained, not merely named.

This is a strong use of chemistry terminology because it explains the process mechanistically. The student shows understanding by connecting ion exchange, hydroxyapatite, and fluorapatite rather than relying on vague description.

The application of source material becomes weaker here because the model system is treated as chemically equivalent to enamel. The student should distinguish between a useful proxy and a direct substitute, otherwise later conclusions about enamel and remineralization become overstated.

The chemistry is mostly correct, but the repeated use of the same concentration language would be stronger if it explicitly linked pH to reaction rate and dissolution of calcium carbonate. The student should avoid describing pH as something that itself “reacts” and instead focus on the ions it represents.

How does this percentage actually demonstrate remineralization rather than simply reduced dissolution or greater mass retention? A more cautious interpretation would strengthen the scientific accuracy of the report.

The student shows the calculation transparently, which makes the data processing easy to follow and check. This is good analytical practice because the reader can see how the final values were obtained from the raw measurements.

The formula uses absolute values, so it cannot show whether mass increased or decreased. Because the report later interprets “mass decrease,” the student should define the direction of change more carefully or use a signed percentage change formula.

The processed table brings together several useful measures in one place, which supports comparison across conditions. Including mean, spread, and uncertainty helps the analysis move beyond raw data toward interpretation.

There is an internal inconsistency between the figure caption and the table below, which is labelled “Type III Sum of Squares.” The student should make the ANOVA reporting consistent, because the choice of sum-of-squares type affects how the analysis is interpreted.

The statistical interpretation is not fully correct here: when $p<\alpha$, the null hypothesis is rejected, not “accepted” or “proved false” in a literal sense. The student should use consistent hypothesis-testing language throughout the analysis.

Does partial eta squared really mean that only random error explains the remaining variation? The student may want to reconsider whether other uncontrolled factors, especially the different mouthwash formulations, could also contribute to the variance.

The conclusion goes beyond what the experiment directly measured. The data show retained eggshell mass, not fluorapatite formation or tooth enamel remineralization. The student should rephrase this as an association between the tested treatments and eggshell mass retention.

This is a thoughtful comparison, but it still treats the mass change as direct evidence of demineralization in enamel. The student should keep the argument tied to the model system and avoid extending the conclusion to tooth enamel without qualification.

The report is organized into a clear sequence of sections that mirrors a formal investigation. This helps the reader navigate the argument from introduction to conclusion efficiently.

The contents page reveals a numbering inconsistency, as the report jumps from section 2.5 to 3 without showing earlier sub-sections in a fully consistent sequence. The student should check all section numbers so the structure is easier to follow.

This method step is difficult to follow because it refers back to the wrong step numbers and mixes the control with commercial products in a way that obscures the design. The student should rewrite the sequence so each condition is listed once, in a consistent order, with clear replicate counts.

The results table is positioned logically before the processed-data discussion, which supports readability. This sequencing helps the reader move from raw observations to summarised data without confusion.

The table is comprehensive, but the label would be clearer if the unit and variable names were formatted more consistently. The student should also ensure that every calculated column is clearly defined in the accompanying text so the reader can interpret the table without guesswork.

This label is inconsistent with the rest of the report, which uses “natural lemon juice.” The student should use one term consistently throughout tables, graphs, and captions so the presentation does not suggest a different variable.