IB Chemistry SL Internal Assessment Example

You framed your investigation in a specific and relevant chemical context, linking hardness to Ca2+/Mg2+ ions, scaling, soap efficiency, and EDTA titration.

You identified the three water sources clearly and explained why comparing them was meaningful.

Your procedure is mostly detailed enough to follow, with fixed volumes, buffer use, indicator use, and repeated trials.

The EDTA solution is treated as if its concentration is known from preparation alone, but it should be standardized to improve reliability.

Some method details that affect reproducibility are still missing, especially sample collection and storage conditions.

Your control of variables is thoughtful, but several entries remain general rather than fully operational.

The endpoint description still leaves room for observer judgement, so it is not yet fully precise.

Your raw data and processed results are organized clearly by sample source and trial number.

You show a worked example of the hardness calculation, which makes your processing easy to follow.

You use the accepted stoichiometric relationship and convert your results into hardness units that suit the investigation.

Your uncertainty treatment is not yet fully rigorous, especially in how uncertainties are combined and carried through to the final hardness values.

The graph would be clearer if the meaning of the error bars were stated explicitly.

The raw burette data are not presented with enough precision to show the titre calculation transparently.

There are a few notation and precision issues that reduce the overall clarity of the analysis.