CAIE IGCSE Chemistry 0620 Theory: Experimental Techniques and Chemical Analysis

Measurement

Variables & Apparatus

• Time: min/sec, measured with a Stopwatch
• Temperature: Celsius, measured with a Thermometer
• Mass: grams, measured with a Balance

Measuring Volume

• Liquids:
  • Measuring Cylinder: For approximate measures
  • Volumetric Pipettes: For fixed volumes
  • Burettes: For variable volumes
• Gases:
  • Gas Syringe: Measures volume gradually

Mixture of Substances

• Mixture: Combination of two or more substances not chemically bonded.
• Solution: Solute(s) dissolved in a solvent.
• Saturated Solution: Maximum solute concentration at a given temperature.

Acid-Base Titration

• Acid added to base until neutralization.
• Use of indicators to observe color changes:
  • Thymolphthalein: Colorless in acid/neutral, Blue in base
  • Methyl Orange: Red in acid, Orange in neutral, Yellow in base

Filtration

• Separates insoluble solid from liquid using filter paper and a funnel.

Crystallisation

• Separates dissolved solid by increasing concentration as the solvent evaporates.
• Crystals formed and purified by washing and drying.

Simple Distillation

• Separates solvent from a solution by evaporating and condensing the solvent.

Fractional Distillation

• Separates miscible liquids using boiling point differences and a fractional column.

Chromatography

• Separates substances based on solubility in a solvent.
• Interpretation: Number of spots equals number of substances.
• Retention Value (Rf): Used to identify substances.

Locating Agents

• Used to visualize colorless chromatograms by drying and spraying with an agent.

Separation Techniques

• Use appropriate solvent, filtration, or magnetic properties to separate components.
• Examples:
  • Solid-Solid: Sand and Salt by dissolution
  • Insoluble Solid-Liquid: Copper (II) Oxide and Water by filtration
  • Soluble Solid-Liquid: Copper (II) sulfate from water by crystallization
  • Liquid-Liquid: Ethanol & Water by distillation or fractional distillation

Purification

• Purity Assessment:
  • Pure substances have a definite melting/boiling point.
  • Impure substances have altered melting/boiling points.

Identification of Ions and Gases

Test for Cations

• Aluminum (Al3+): White precipitate with NaOH, colorless in excess.
• Copper (Cu2+): Light Blue precipitate with NaOH, Dark Blue with excess NH3.
• Zinc (Zn2+): White precipitate, soluble in excess.

Test for Anions

• Carbonate (CO): Effervescence with dilute acid.
• Chloride (Cl): White ppt with silver nitrate.
• Sulfate (SO): White ppt with barium nitrate.

Gas Tests

• Ammonia (NH3): Red litmus turns blue
• Carbon Dioxide (CO2): Turns limewater milky
• Hydrogen (H2): Squeaky pop with lighted splint

Flame Tests

• Lithium: Red flame
• Potassium: Lilac flame
• Copper (II): Blue-Green flame

Organic Chemistry

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