Mixtures

Traps in Mixtures

• Chooses the wrong separation technique
  Insoluble solid + liquid: filtration. Dissolved solid: evaporation/crystallisation. Miscible liquids: fractional distillation. Immiscible liquids: separating funnel. Dyes: chromatography. Sublimable solid (iodine, NH₄Cl): sublimation.
• Puts a substance or reaction in the wrong class
  Classify from the defining feature: functional group for organic series; bond type and structure for properties; reaction with acid AND alkali for amphoteric. Check each option against the feature, not the name.
• Chooses a true but irrelevant statement
  Re-read the question word (why, which, what causes). A true fact that answers a different question is still wrong.
• Confuses elements, compounds and mixtures
  Element: one kind of atom. Compound: elements chemically combined in fixed proportions, new properties (water, NaCl). Mixture: components not chemically combined, variable composition, separable physically (air, sea water, brass).
• Takes one factor as the whole answer
  Ask whether the option is necessary or sufficient. If the stem involves two changes or two conditions, both must appear in the answer.