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8.2Laboratory Skills

Separation and analysis — EST 2 Chemistry Revision Notes & Topical Questions

5 min read 8 parts Lesson 2 of 2 1 quiz

📚 EST 2 Chemistry Hub / Topical Revision
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Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
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Lesson summary

Separation and analysis EST Chemistry notes: Select separation techniques.A pure substance gives a single spot in chromatography.Rf is always between 0 and 1.Impurities lower and broaden melting point range.Water enters a condenser at the bottom for efficient cooling.Centrifugati…

  • A spot travels 3.0 cm; solvent front travels 7.5 cm. Find Rf
  • Separation and analysis EST Chemistry: what to do next
  • Filtration
  • Evaporation
  • Crystallisation
  • Distillation

Part 1 of 8Key ideas

1
A pure substance gives a single spot in chromatography.
2
Rf is always between 0 and 1.
3
Impurities lower and broaden melting point range.
4
Water enters a condenser at the bottom for efficient cooling.
5
Centrifugation separates suspended solids by spinning.

Part 2 of 8Learning objectives

Learning objectives
Select separation techniques.
Calculate Rf values.
Describe tests for purity and identity.

Part 3 of 8Essential knowledge

1
Draw the baseline in pencil (ink would run).
2
Keep the baseline above the solvent level.
3
Distillation depends on differences in boiling point.
4
Gas chromatography separates volatile mixtures.
5
Precipitation tests identify ions (e.g., Ag+ for halides).

Part 4 of 8Process & sequence

1
Identify the physical difference between components.
2
Choose a method exploiting that difference.
3
Perform the separation.
4
Test purity (melting point, chromatography).
5
Identify using analytical techniques.

Paper chromatographywrite these steps in this order; each step is a marking point.

  1. Pencil baseline
  2. Spot sample
  3. Solvent rises
  4. Components separate
  5. Calculate Rf

Part 5 of 8Worked examples

  1. A spot travels 3.0 cm; solvent front travels 7.5 cm. Find Rf.

Part 6 of 8Summary

Summary
Separate by physical property.
Rf = spot ÷ solvent front.
Pure solids melt sharply.

Part 7 of 8Keep going

Separation and analysis EST Chemistry: what to do next

These Separation and analysis EST Chemistry notes covered the key ideas, worked examples and exam technique for this topic. Check your Separation and analysis EST Chemistry understanding with the practice questions below, then reread any Separation and analysis EST Chemistry point you were unsure about before moving on.

1
Practice: Separation and analysis EST Chemistry practice questions
2
Previous lesson: 8.1 Practical technique and safety
3
Course: EST 2 Chemistry — all units
4
Official syllabus: OpenStax free science textbooks

Separation and analysis EST Chemistry revision notes

Part 8 of 8Compare: Compare

Choosing a method
MixtureMethod
Sand + waterFiltration
Salt from salt waterEvaporation / crystallisation
Pure water from sea waterSimple distillation
Ethanol + waterFractional distillation
Dyes in inkPaper chromatography
Iron + sulfur powderMagnet
Oil + waterSeparating funnel
Analytical techniques
TechniqueInformation
Mass spectrometryMolar mass, isotopes
IR spectroscopyFunctional groups (bond vibrations)
Flame test / emissionMetal ions
Melting pointPurity (pure: sharp; impure: lower, broad)
TitrationConcentration

Key terms

Command terms

Command terms
Identify / Describe (FRQ)
A short, specific statement; describing requires relevant characteristics, not a single word.
Explain / Justify (FRQ)
Give the cause-and-effect reasoning or evidence; a restated fact does not score.
Calculate
Show setup, substitution and the answer with units.
Predict
State the expected outcome; add a reason only if asked to justify.
MCQ technique
Read every option; eliminate distractors that are true statements but do not answer the question; watch for NOT/EXCEPT.

Exam technique

Keywords the mark scheme looks for in this lesson

Keywords the mark scheme looks for in this lesson
Filtration · Evaporation · Crystallisation · Distillation · Fractional distillation · Chromatography · Rf value · Spectroscopy
Learn each definition in the Key words tab exactly; a missing keyword in a definition usually loses the mark.

How to get full marks (examiner guidance)

1
Answer exactly what is asked; extra correct material does not earn credit, and contradictory statements can cancel credit (AP FRQ).
2
Use precise vocabulary (e.g. “active site”, “concentration gradient”, “allele”), never “it/stuff/things”.
3
Show units and working in calculations.
4
In MCQs, predict the answer before reading the options, then eliminate.

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