# Practical and investigative skills

> IB Chemistry HL · IB Chemistry HL
> Source: https://www.owlsprep.com/study/ib-chemistry-hl-u7-overview/
> Weight: n/a

This unit covers all core practical skills required for IB Chemistry HL, from experimental planning to completing your graded internal assessment (IA), which counts for 20% of your final IB Chemistry score.

**Prerequisites:** Completion of all prior IB Chemistry HL core units; Basic understanding of SI units and standard measurement

## Learning objectives

- Design valid, controlled chemistry experiments aligned with clear testable research questions
- Correctly collect, process and interpret both qualitative and quantitative experimental data
- Identify, classify and quantify different types of error and uncertainty in experimental work
- Structure a complete IB Chemistry internal assessment that meets all official marking criteria

## Unit at a glance

Practical chemistry is the foundation of chemistry as an experimental science, and this unit builds transferable skills you will use for both exam questions and your mandatory internal assessment. The learning arc progresses logically from planning an experiment through processing data, analyzing error, drawing conclusions, and finally breaks down all IA requirements.

Each subtopic builds directly on the previous one: you cannot correctly analyze data without first designing a controlled experiment, and you cannot draw a valid conclusion without properly accounting for experimental uncertainty. These skills are applied across all other units of IB Chemistry.

The following subtopics make up this unit:
- [Experimental design](https://www.owlsprep.com/study/ib-chemistry-hl-u7-experimental-design/) — Learn to write testable research questions, control variables, and plan safe, appropriate experimental methods.
- [Data collection and processing](https://www.owlsprep.com/study/ib-chemistry-hl-u7-data-collection-and-processing/) — Master recording qualitative/quantitative data, converting units, and processing raw data into usable results.
- [Graphical analysis and error estimation](https://www.owlsprep.com/study/ib-chemistry-hl-u7-graphical-analysis-and-error-estimation/) — Construct meaningful graphs, propagate error, and calculate uncertainty in final experimental results.
- [Scientific reasoning and conclusion drawing](https://www.owlsprep.com/study/ib-chemistry-hl-u7-scientific-reasoning-and-conclusion-drawing/) — Evaluate whether data supports your hypothesis, and identify key limitations of your experimental design.
- [Internal assessment requirements](https://www.owlsprep.com/study/ib-chemistry-hl-u7-internal-assessment-requirements/) — Break down IB's IA marking criteria, and learn how to structure your IA report for full marks.

## Common pitfalls

- **Wrong:** Confusing random error with systematic error when evaluating experiments
  - Why it fails: This leads to incorrect improvement suggestions, costing marks in both exams and the IA
  - Correct: Attribute inconsistent variation to random error (reduced by repeats) and consistent bias to systematic error (reduced by better calibration)
- **Wrong:** Leaving multiple key variables uncontrolled in an experimental design
  - Why it fails: This makes it impossible to isolate the effect of the independent variable on your outcome
  - Correct: Explicitly list all controlled variables and describe how they are kept constant during the experiment
- **Wrong:** Ignoring uncertainty when drawing conclusions from data
  - Why it fails: This can lead to false claims of trends or correlations that are not supported by your results
  - Correct: Always compare the magnitude of uncertainty to the size of your measured effect when concluding

## Cheatsheet

| Key Concept/Formula | Description |
| --- | --- |
| $\%\ Uncertainty = \frac{Absolute\ uncertainty}{Measured\ value} \times 100$ | Calculate percentage uncertainty for a single measurement |
| Total uncertainty = Sum of absolute uncertainties | Rule for combining uncertainty with addition/subtraction |
| Total % uncertainty = Sum of individual % uncertainties | Rule for combining uncertainty with multiplication/division |
| Independent variable | Variable intentionally changed in an experiment to test its effect |
| Dependent variable | Variable measured to assess the effect of the independent variable |
| Controlled variable | Variable kept constant to avoid confounding experimental results |
| Random error | Unpredictable measurement variation, reduced by repeated trials |
| Systematic error | Consistent measurement bias, reduced by improved equipment or procedure |
| IA Criterion: Evaluation | Worth 6 marks, assesses your analysis of error and experimental limitations |
| IA Criterion: Personal Engagement | Worth 2 marks, assesses your personal input and interest in your topic |

## What's next

Begin your study of this unit with the first subtopic on experimental design, which lays the foundation for all other practical skills you will build in this unit. Mastering this first topic will make it easier to understand subsequent concepts around data processing, error analysis, and internal assessment. Once you complete all subtopics in this unit, you are ready to move on to the next unit of IB Chemistry HL covering additional higher-level topics.

- [Experimental design](https://www.owlsprep.com/study/ib-chemistry-hl-u7-experimental-design/)
- [Data collection and processing](https://www.owlsprep.com/study/ib-chemistry-hl-u7-data-collection-and-processing/)
- [Graphical analysis and error estimation](https://www.owlsprep.com/study/ib-chemistry-hl-u7-graphical-analysis-and-error-estimation/)

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