Non-metals

Traps in Non-metals

• Reverses a trend, direction or effect
  State the rule with its direction before looking at the options (down group 1 reactivity INCREASES; exothermic forward reaction: heating shifts LEFT). An option that is the mirror image of the rule is the trap.
• Picks a related substance or process with a different role
  Learn reagents and processes as one-line 'name → job' cards and contrast neighbours in a table (process | product | catalyst | conditions). Match the job in the stem, not just the topic.
• Uses everyday or macroscopic thinking instead of particles
  Ask what the particles, ions or electrons are doing. Properties of a substance come from its particles and bonds, not from how it looks or feels.
• 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.
• Thinks a catalyst shifts equilibrium, adds energy or is used up
  A catalyst gives an alternative route with lower activation energy for BOTH directions. It is unchanged at the end, so it changes the rate only: never the yield, ΔH or Kc.
• Properties of hydrogen/oxygen/water errors
  H₂: Zn + dilute acid; collected over water or by downward displacement of air; burns with a pop. O₂: decomposition of H₂O₂ (MnO₂ catalyst) or KClO₃; relights a glowing splint. NH₃ collected by upward delivery (less dense than air); HCl, CO₂ by downward delivery.
• Confuses tests for gases
  CO₂ turns limewater milky; H₂ gives a 'pop' with a lighted splint; O₂ relights a glowing splint; NH₃ turns damp red litmus blue; Cl₂ bleaches damp litmus.
• 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.
• Mixes up a pair of similar chemical terms
  Keep a list of confusable pairs with one defining feature each and a hook. Underline the key word in the stem and check it against the definition, not the sound of the name.
• Periodic trend errors
  Across a period: radius decreases, ionisation energy and electronegativity increase (more protons, same shell). Down a group: radius increases, ionisation energy decreases (more shells, more shielding).
• 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.