What Makes a Substance Pure?
Part of Purity & Formulations — GCSE Chemistry
This deep dive covers What Makes a Substance Pure? within Purity & Formulations for GCSE Chemistry. Revise Purity & Formulations in Chemical Analysis for GCSE Chemistry with 20 exam-style questions and 12 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 2 of 13 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 2 of 13
Practice
20 questions
Recall
12 flashcards
🔬 What Makes a Substance Pure?
In everyday language, "pure" means natural or without additives — "pure orange juice" or "pure wool".
In chemistry, a pure substance contains only ONE type of element or compound. Nothing else. Not even a tiny trace of another substance.
Examples of Pure Substances
- Elements: Pure copper (Cu), pure gold (Au), pure oxygen (O₂)
- Compounds: Pure water (H₂O), pure sodium chloride (NaCl), pure carbon dioxide (CO₂)
Examples of Impure Substances (Mixtures)
- Tap water: Contains dissolved salts, chlorine, fluoride
- Air: Mixture of nitrogen (78%), oxygen (21%), other gases
- Brass: Mixture of copper and zinc
- Orange juice: Mixture of water, sugars, acids, vitamins
Quick Check: Is distilled water a pure substance in the chemical sense?
Yes — distilled water contains only H₂O molecules. It is a pure compound.