# Experimental Techniques and Chemical Analysis

> CIE IGCSE Chemistry · CIE IGCSE Chemistry (0620)
> Source: https://www.owlsprep.com/study/cie-0620-u12-overview/
> Weight: 15-20% of MCQ, theory, and practical assessment papers

This unit covers core practical chemistry skills required for all IGCSE assessments, including apparatus use, mixture separation methods, and qualitative analysis of ions and gases. It forms the foundation for Paper 6 practical exam content.

**Prerequisites:** [States of matter and mixture fundamentals (Unit 1)](https://www.owlsprep.com/study/cie-0620-u01-overview/)

## Learning objectives

- Select and use standard laboratory apparatus for accurate measurements and quantitative procedures like titration
- Apply appropriate separation, purification, and chromatography techniques to process and identify mixture components
- Carry out standardized qualitative tests to identify common cations, anions, and gases in unknown samples
- Evaluate experimental accuracy and identify common sources of error in practical investigations

## Unit at a glance

You will begin with foundational measurement and titration skills, critical for reliable quantitative practical work, before moving to separation and purification methods for different types of mixtures. The unit concludes with qualitative analysis test protocols you will use to identify unknown chemical samples in both theory and practical assessments.

Work through the following subtopics in order to build practical proficiency step-by-step:
- [Apparatus, Measurement and Titration Technique](https://www.owlsprep.com/study/cie-0620-u12-apparatus-measurement-and-titration-technique/) — Learn to select appropriate lab apparatus, take precise measurements, and perform acid-base titrations accurately.
- [Separation, Purification and Chromatography](https://www.owlsprep.com/study/cie-0620-u12-separation-purification-and-chromatography/) — Master common separation techniques (filtration, distillation, crystallisation) and interpret paper chromatography results.
- [Identification of Ions and Gases (Qualitative Analysis)](https://www.owlsprep.com/study/cie-0620-u12-identification-of-ions-and-gases/) — Memorise standard qualitative test procedures and key observations for identifying common ions and gases.

## Common pitfalls

- **Wrong:** Using a measuring cylinder for titration volume measurements
  - Why it fails: Measuring cylinders have high measurement error, leading to unreliable and imprecise titre values
  - Correct: Use a burette for adding titrant and a volumetric pipette for measuring fixed volumes of analyte
- **Wrong:** Assuming all visible spots on chromatography paper are pure compounds
  - Why it fails: Mixtures of similarly structured coloured compounds may not separate fully under standard solvent conditions
  - Correct: Compare calculated $R_f$ values against known pure reference samples run on the same chromatography paper
- **Wrong:** Using a glowing splint to test for carbon dioxide
  - Why it fails: A glowing splint only identifies oxygen; CO2 will extinguish it, but so will many other non-flammable gases
  - Correct: Use limewater, which turns milky in the presence of carbon dioxide, to confirm the identity of the gas

## Cheatsheet

| Rule/Formula | Use Case |
| --- | --- |
| Titration calculation: $\frac{M_1V_1}{n_1} = \frac{M_2V_2}{n_2}$ | Calculate unknown concentration of acid/alkali from titre values |
| $R_f = \frac{\text{Distance moved by substance}}{\text{Distance moved by solvent front}}$ | Identify unknown compounds from chromatography results |
| Ammonium test: Warm sample with NaOH, test gas with damp red litmus | Detect $NH_4^+$ ions (litmus turns blue if present) |
| Sulfate test: Acidify with dilute $HNO_3$, then add $Ba(NO_3)_2$ solution | Detect $SO_4^{2-}$ ions (white precipitate forms if present) |
| Hydrogen test: Hold lit splint near open test tube mouth | Detect $H_2$ gas (squeaky pop sound occurs if present) |

## What's next

Start your learning with the first subtopic on apparatus, measurement, and titration to build foundational practical skills you will apply across all subsequent experimental work. Once you complete this full unit, you will progress to the chemical energetics unit, where you will apply your measurement skills to enthalpy change experiments.

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From [OwlsPrep](https://www.owlsprep.com) — free study guides for A-Level, IB, AP and IGCSE, written against the official syllabus. Canonical page: https://www.owlsprep.com/study/cie-0620-u12-overview/