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Updated Mar 16, 2026

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2 pages

Chemical Analysis Explained: Practice Questions and Answers

Sophia + Charlotte

@sophia.lily06

Chemical analysis is everywhere around you - from testing water... Show more

Mixtures & Formulations

Understanding the difference between elements, compounds, and mixtures is crucial for chemical analysis. Elements like oxygen and titanium contain only one type of atom, whilst compounds like methane and carbon dioxide have different atoms chemically bonded together.

Mixtures such as air and seawater contain different substances that aren't chemically joined. A special type of mixture called a formulation is designed for a specific purpose - think paint, which combines pigments, solvents, and binders to create the perfect coating.

Pure substances in chemistry have sharp melting points, but mixtures melt over a range of temperatures. You can separate mixtures using different techniques: filtration for sand and water, distillation for alcohol and water, and evaporation for salt and water.

Quick Tip: Remember that "pure" in chemistry means only one substance - not the everyday meaning of "clean"!

Chromatography separates mixtures based on how soluble different components are. The least soluble substances travel the shortest distance up the paper. Always draw your start line in pencil (never ink!) and keep it above the water level to get accurate results.

Identifying Ions and Testing Gases

Flame tests give you a quick way to identify metal ions by their distinctive colours. Lithium burns crimson, sodium gives a bright yellow flame, and potassium produces a lovely lilac colour. However, mixed samples can be tricky since colours blend together.

For more detailed analysis, you'll use sodium hydroxide to test for positive metal ions. Most form coloured precipitates (solid particles that form in solution) - copper gives blue, iron(II) makes green, and iron(III) produces brown. Aluminium is special because its white precipitate redissolves with excess sodium hydroxide.

Negative ions need different tests entirely. Halide ions (chloride, bromide, iodide) react with silver nitrate to form white, cream, or yellow precipitates respectively. Sulfate ions form a white precipitate with barium nitrate.

Remember: Each gas has its own unique test - hydrogen pops with a lit splint, oxygen relights a glowing splint, carbon dioxide turns limewater cloudy, and chlorine bleaches litmus paper.

Gas tests are straightforward once you know the tricks. Adding acid to carbonates releases carbon dioxide, which you can identify by bubbling it through limewater.

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Chemistry

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808

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Updated Mar 16, 2026

•

2 pages

Chemical Analysis Explained: Practice Questions and Answers

Sophia + Charlotte

@sophia.lily06

Chemical analysis is everywhere around you - from testing water quality to identifying unknown substances in forensic investigations. This topic covers the essential techniques chemists use to separate mixtures, identify elements and compounds, and test for specific ions and gases.

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Mixtures & Formulations

Quick Tip: Remember that "pure" in chemistry means only one substance - not the everyday meaning of "clean"!

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Improve your grades

Join milions of students

Identifying Ions and Testing Gases

Remember: Each gas has its own unique test - hydrogen pops with a lit splint, oxygen relights a glowing splint, carbon dioxide turns limewater cloudy, and chlorine bleaches litmus paper.

Gas tests are straightforward once you know the tricks. Adding acid to carbonates releases carbon dioxide, which you can identify by bubbling it through limewater.