Separation techniques
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Flip to reveal answersWhy can mixtures be separated physically?
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All 12 Flashcards — Separation techniques
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Question
Why can mixtures be separated physically?
Answer
Their components are **not chemically bonded**, so they keep their own properties and can be separated by **physical** methods.
Question
What does filtration separate, and how?
Answer
An **insoluble solid** from a liquid — the solid is too large to pass through the **filter paper** (uses particle size).
Question
What does evaporation / crystallisation separate?
Answer
A **dissolved (soluble) solid** from its solution — the **solvent boils off**, leaving the solid behind.
Question
What does distillation separate, and how?
Answer
Liquids (or a liquid from a dissolved solid) by their difference in **boiling point**.
Question
What does chromatography separate, and how?
Answer
The dissolved components of a mixture by their difference in **solubility / attraction** to the paper.
Question
What is the R_{f} value?
Answer
R_{f} = distance moved by **spot** ÷ distance moved by **solvent** — a ratio with **no units**, between 0 and 1.
Question
What does a larger R_{f} tell you?
Answer
The component is **more soluble** in the solvent, so it was carried **further** up the paper.
Question
How do you recover an insoluble solid like sand from a mixture with salt?
Answer
Add water to dissolve the salt, then **filter** — the sand stays as the residue.
Question
How do you separate iron from a sand/salt mixture?
Answer
Use a **magnet** — iron is **magnetic**, sand and salt are not.
Question
Best technique to purify a solid product made in solution?
Answer
**Crystallisation** — dissolve in hot solvent, cool to form pure crystals, then filter them off.
Question
Can an R_{f} value be greater than 1?
Answer
**No** — the spot cannot move further than the solvent front, so 0 < R_{f} < 1.
Question
Match the property to the technique.
Answer
Size → **filtration**; boiling point → **distillation**; solubility → **crystallisation / chromatography**.
Read the notes
Full study notes for Separation techniques
Topic 1.1 hub
Introduction to the particulate nature of matter
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Chemistry exam skills
Paper structures & tips
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